Private ceremony & open reception on another date

70 people isn’t small. This seems really weird to me.

There is no polite way to word an impolite wedding invitation. Sorry, wish I could help.

Send two separate invites. One that clearly states it is for the ceremony (with reception to follow on date). Send that one to the 70 people invited. Send a second invite that clearly states it is for the reception and make sure the style of that invite matches the style of party you are going for.

You are tiering your wedding guests and this is extremely rude and tacky. Have the one ceremony and reception you can afford and leave it at that.

If I got an invite to this 'second string' backyard BBQ all I would think is 'wow they really on the hunt for gifts'

You can fit 300 people in your backyard? Why do you need two receptions (assuming the 70 people are also treated to a special dinner or something).

There are two parts here that are problematic
1) You need to thank your guests for attending the ceremony. Will anyone be traveling for the 70-person ceremony? You need to feed them a meal and provide them with drinks
2) It is considered poor etiquette to not invite everyone to the ceremony that is invited to the reception (unless it is immediate family only)

I think you either need to just have the ceremony as originally planned and host those people immediately with a reception or have the ceremony with only immediate family (siblings, parents, grandparents and SO's) and have the larger party as mentioned.

70 isn't exactly small. If there are friends who aren't making the cut to get to come to your actual ceremony and reception, I'd just leave it at that. For reference, we had 75 guests attend our wedding (myself, DH, and our WP included), and it didn't feel small. We also didn't have any kind of post celebration at a later date.

Edit:
The venue of the wedding is a family lake cottage, there isn’t much space. I come from a broken family so, 70 is actually still cutting out people who I am going to offend but, the venue just cannot hold that many.

I want to celebrate with my other family and friends. I chose a backyard BBQ because it’s cheaper and less formal.

Wouldnt this be the same situation for people that have a destination wedding and then a reception at home? I don’t want to be rude to anyone, that’s why I’m asking for advice before I start making real plans.

I do know I probably cannot have a shower because that would be rude to invite people that are not invited to the wedding.

View Quoted Comment 70 is just Family and 5 close friends.

mom, dad, step mom, ex step dad, ex step dads new wife, all of my grandparents (10), siblings (10), and a few of my aunts, uncles, and cousins. I am extremely close to my family. I cut it down as best as possible.

View Quoted Comment Possibly, if your wedding is also a DW. Is the lodge really far away? Do people need to book plane tickets to get there.

We got married in DE and we were living in AZ. We still didn't see the need to plan any kind of at-home reception for those who couldn't make it or weren't invited.

View Quoted Comment Immediate family would be your children, parents, step parents, and siblings only. You have 70 people who are immediate family?

Cut the guest list for the ceremony to just real immediate family. For the reception, a BBQ is fine as long as the ceremony is truly only immediate family. Catering and bar service are going to be very very very costly for this number of people, just to warn you.

View Quoted Comment Technically it’s a destination w doing but everyone can stay at the family lake cottages. So they will just drive about 2 hours. But it isn’t big enough for anyone over the 70. ):

View Quoted Comment Second this.

eta: if people are driving 2 hours there and back you will need to provide them with a meal for this also. Hosting 70 people and then 300 people later on is going to be very expensive. Can you look for a venue that will be able to host ceremony & reception & maybe take another look at your guest list? 300 people is really a lot.

View Quoted Comment A 2 hour drive really isn't a destination wedding. It's OOT, sure, but not really a prohibitive distance where it's unrealistic for people to make the trip. It's simply a little out of the way.

The only way you can pull off a "private" ceremony and large reception later is if the ceremony is under 20ish people, imo. If I were you I would take that list of 70 (bump it up to 100 if you want more friends there) and do a wedding with reception immediately after. If cost is an issue then cut the aunts, uncles and cousins. Just take your siblings, parents and grandparents out to dinner.

I think if you are honest about the restrictions of the venue and explain that while you would love to invite everyone, but it isn't physically possible, and then always term the secondary party as a party and not a "wedding reception", it should be fine. I don't expect to bring gifts to every party I attend, so with the right wording, you will be fine.
A cousin of my FH is doing this. They are having a small wedding (nearest and dearest). When they get back from their honeymoon, they are having a party. None of us invited to the party only think they expect a gift, and we understand their point. My FH and I especially understand the desire to keep things small since our 80 person wedding is running us between 40k and 50k. It never once crossed any of our minds (mine, FH and FH 10 person family, all party only invites) that what they were doing was rude or "tiered". Just be open and honest.

View Quoted Comment But if they aren't your nearest and dearest, why even throw a 2nd party? I don't understand the point of celebrating a wedding you weren't asked to witness other than for a true DW or an immediate family only ceremony.

eta: and if they ARE your nearest and dearest, why not find a venue that can accommodate them? Isn't that more important?

View Quoted Comment

This. ^^^^^

You should either keep the venue you've chosen and skip the bbq later or find another venue that will accommodate more people.

Did you send out STDs? How did you word those?

I had a DW with about 80 people. I did not do a party back home afterwards because IMO it would have been rude and gift grabby.

I say stick to one of the options. Either you have the 70 people that you adore or the 300 that you want. If it's important to you to have that many people then maybe think about a different venue that can hold more than 70 people.