Find other parents of school friends, etc. and let him sleep over their house; I'm sure their parents would like the favor returned.

Maybe make a special place for the 5 year old to be to watch TV or special movies on a quilt in the living room?

Can you all do a night out together, get a sitter for the 5 year old (or trade with a friend with a young child).

Can his grandparents take him for a weekend or a favorite aunt/uncle?