J.C.
as others have said; too young for waterslide and definitely not worth the expense at two. Unless you have specific kids that he absolutely loves to be with.. he really doesn't need a "friends" or kids party at 2. I would take the family and go to the beach for the day. Or a local pool. Then cake and ice cream later and you are done! there are plenty of birthday parties to come... take a break when they don't know anything different yet!
enjoy -- J..
P.S. - my daughter will be seven 8/24.. and I still haven't rented one of those waterslides... each year she wants something else! LOL