That is the way we had birthday parties too, and they are the best. Invite the whole family not just the kid. Nobody HAS to drink, and I didn't because hosting, but it's more hospitable to have adult beverages available. Often a "fancy drinks" area for the kids too, with colorful non alcoholic drinks and garnishes for them to create their own drinks.

So, so much better than a house full of kids all the same age. Kids running around in packs, adults chilling.