Chocolatebubbles YANBU at all. You sound like a woman who has an unpleasant over bearing MIL and a husband who doesn't understand.
There is no way I'd want my MIL ever babysitting for me if she had threatened to not give my baby back. That is vile.
I agree with donquixotedelamancha don't sweat the small stuff. Decide with your dh what to do. agree to whatever is a compromise and then just go with it.
In your shoes, for me, it would be to have a party in a pub/restaurant/ caterered room where I would not be doing any clearing up! I would not be doing any running around.
The idea you have to do the same is a bit odd! We did similar. When dd was dedicated (similar to baptism) we were going to a big church with a big posh hall. We hired on some ladies from church for the food and had a lovely lunch afterwards, I think with alcohol.
When ds was dedicated over 9 years later we were in a smaller church with a decidedly ropier church hall! We invited a lot of people with kids do we chose not to have alcohol. Some of our friends at church helped us cater and we had a less 'posh' meal with kids acrivites. Dd was dedicated as a baby, ds as a four year old.
Anyway, it sounds like it is hard to reconcile your and your dh's plans so find a way to have a party and maybe say to dh you will take baby home early for a nap if it is too much for to be around do many people for you or baby.