Well as it turns out we didn't need that much food after all! My in laws are both very allergic to cats though FIL is worse than MIL. When he comes over he will sit on the porch the whole time and if he comes inside at all it's for maybe about 5 minutes at most. But we were happy that they came to the baptism so we were okay and understanding of them not coming to the house.
My brother and girlfriend didn't come back to the house either as they had other plans for Mother's Day, which is also fine. I kind of expected that with it being that holiday, people would be busy and it worked out pretty well in the end, as it gave us time to eat and pack up the van and get on the road earlier than we had expected to. So DH had plenty of ham left to eat for the rest of the week!
I also discovered a potato salad I actually like! I got it from Martin's, a red skinned potato salad that I think must have had some dill in it as well.