Large family

Are you inviting friends as well? Maybe your fiancée could invite more friends than you do so that it is a little more even? But even if there is a big difference in the guest list, I don't think it will really matter. I've been to a few weddings where one half of the couple has had a much larger number of guests than the other (usually where one partner is from overseas, so they don't have so many people able to attend) and it hasn't really been noticeable. As long as you mix up the tables at your reception and don't have designated bride and groom 'sides' at the ceremony, no one is likely to even realise the imbalance.

It’s okay as long as both families are equally included. Speeches, readings, key roles etc., as long as they feel evenly distributed, it’ll all be fine.
My husband had 2 members of family attend our wedding, where as I had 10. In contrast he has this big friends group of 8 guys (plus 4 of them have partners) that he has been friends with since he was in primary/high school and so his Mum & Sister knew a lot of them, and they are by extension “like a family”. My friends are all either small groups or “one-off” friends, and my family knew only a couple of them. It all works itself out as long as you’re conscious of job roles/special parts/seating plan etc., which given you’re already thinking about it, you sound like it’ll all be fine, and hopefully everyone will have a lovely day celebrating you both and the families coming together.