My sons birthday is in August so Florida weather dictates either an inside party, or a "cool" outdoor one.  His 2nd birthday party also happened to come at the peak of my sons "water" obsession. As we do not have a swimming pool, we had to get creative in order to accommodate his interests. We decided to host an "Everything Wet" party.  We sent our invitations printed on computer paper with tropical fish and water.  There are lots of different ones out there.  They read " Summer's hot, Oh what to do? Come cool off with a boy who's two!" "Join us for a splishy, splashy, birthday party."  Invitation instructed kids to bring a swimsuit and towel. We rented a water slide from the local party place.  Kids were able to climb up the back and slide down.  it was big enough for adults too. That came in handy with the real little ones.  We also filled my sons sandbox with water to act as a kiddy pool for the babies.  A slip and slide, or sprinkler would work as easily and more economically. We served fried chicken, potato salad, and baked beans. (Picnic food)  I served the potato salad, and beans in sand pails, with shovels to serve. I used beach towels as the tablecloth, and as extra seating for adults. Balloons in bright, tropical colors, tropical fish Mylar balloons, and beach chairs served as decorations.  His cake was designed by Publix.  It was a board with clear gel blue icing (water) with tropical fish cakes nestled on top.  Green icing acted as seaweed.  Favors were a beach pail with snack treats, water squirters, sunglasses, and cookies shaped like fish. All were personalized with paint pens. Children and parents went home full, and tired!