Invitations for Groom's Parents Home

So we are having a courthouse wedding/elopement followed by a very low key reception. Everything is being paid for by us, the bride and groom, but my FH's parents have a beautiful backyard that they offered us to use for the reception. My mother (MOB) finds this mortifying. She offered to pay for the wedding and reception, but only if I did everything her way (very conventional to please her and cheap to please my dad), so we declined. She withdrew financial support in a huff but is now begging me to not have a reception or not at the groom's parents house or not in my wedding dress because she thinks it will look bad for her. I am mystified by all of this. My FH and I are very casual people. We don't want a procession, or to do vows in front of the like... 30-40 people we know. We have also in our late thirties and have been dating for 10 years. We just want to sign some documents and have a chill backyard party with close friends and family. We will get a tent in case of rain and rent tables and chairs and linens. We will provide food and alcohol and have an instax guestbook and party favors--basically, the stuff we like. We questioned the need for formal invitations but figured it is relatively inexpensive and also curtails people doing invites on our behalf (like... it's informal but not an open invite BBQ).


I am concerned about my mother carrying on about the ettiqute and choosing not to come but I can't really do anything about her attitude. For the invites, though, what should the wording look like? I was thinking something like:
Share the Joy
You are invited to celebrate the elopement of BRIDE'S NAME and GROOM'S NAME at
ADDRESS, the childhood home of the groom
Date and Time
Please RSVP by
Website address for more info
This avoids naming his parents without naming mine. It also makes it clear it is just a party, not a wedding. His parents are providing space but not hosting (not paying for anything or doing any labor).
This would all be easier if both families agreed to cohost and chipped in an even amount (not everything, just equal involvement) and then I could put both names on the invite, but we are not there yet.
Wedding is in 4 months.
Any ideas?