ok to break etiquette?

Since you gals are always so helpful, I wanted advice on a tricky situation. I am having a destination wedding in the Fall. I have a huge family (close to 200 people just on my side alone). Once you add in my family, FH’s family, and our friends, our guest list would have been over 300. We both wanted a smaller, more intimate wedding, so we decided on a destination wedding. The venue holds a MAX of 50 people. Obviously there will be A LOT of friends & family who will not get an invite. They are all understanding about this. However, lots of family members keep suggesting we have a reception when we return, so that everyone can celebrate with us in some way. We hadn’t planned on doing one, but we both agree if our family’s are wanting it then we would be happy to host something. The problem is, as soon as we return from the wedding FH goes on-call with work for 5 months. Meaning we cannot leave town for that entire time (family is 4 hrs away and reception would be there) and really can’t plan anything because if he gets called out he has to be there within 30 mins. 5-6 months is a really long time after the wedding to have a reception. I feel like it seems rather silly to have one that long after. I expressed this to my mom & she and 3 of her sisters (my aunts) suggested I have it in September (2 months BEFORE we get married) while all our out of town and out of state relatives are back for an event we do each year. FH and I are totally good with this- we were planning on being there anyway plus it’s super convenient for our out of town family who were planning to be there anyway also, so no need for extra travel- BUT I’ve read in here that it is bad etiquette/rude to invite people to pre-wedding events who aren’t invited to the ceremony. I understand it being rude to invite someone to a shower or bachelor/bachelorette party (we are not having either) then not to the wedding. But under the circumstances, would what my mom & aunts are suggesting be rude?