My uncut son is potty training now, but my husband is cut. Does it make a difference?

No! The foreskin should not change the way a male pees. I do suggest if any son watches his father pee, have dad sit on the toilet. That way he can do it like dad, sitting down, until he's old enough to aim! The biggest difference if his foreskin remains is you need to pull gently back and clean it daily, then teach him to do the same as he gets older. Don't force it if it doesn't pull easily!
Shouldn't matter. During the rehersal & work of this effort it should not matter. The event is an opportunity to point out that people are sometimes different & that is ok, a good lesson for all of us.
Absolutely Not. Being circumcised or not, does not in any way affect training!