FI and I aren't sure what to do about these 2, so I'd appreciate any thoughts

Sorry it's a little long, wanted to try and explain!
We're trying to keep the RD costs down. Us, our parents, WP and S/Os are all definately invited (and that equals about 23 people). However, we're not sure about these 2 sets:
1. My aunt/uncle (also parents of a BM). My aunt has done a TON for the wedding - hosting my shower, making invites, programs, table numbers, helping with centerpeices & bouquets, etc. She offered and I know it's a lot of work. I thought it'd be nice to invite them to the RD to special thanks them for being part of the wedding planning.
2. His aunt/uncle (also parents of a GM - but will be traveling with 2 older daughters and FI's grandmother). They gave us a really nice wedding gift already (use of their timeshare for 12 nights to take a honeymoon) and now just got us a really nice shower gift to boot. FI thinks because of the honeymoon gift they should be at the RD too. He also thinks we could invite just the aunt/uncle and not the other 2 kids and grandma (I disagree). I feel like inviting them is not fair to other people because we're inviting them because they gave a bigger gift and it's a slight to those who don't have those means. All gifts are just as appreciated.
My vote is to invite my aunt/uncle because they participated in planning the wedding and not his aunt/uncle because that's signaling out that they gave a big gift. What do you think?
side note - we were planning to give his aunt/uncle more than just a thank you card after the wedding anyway, maybe a bottle of wine or souveneir of a sort from the honeymoon.