N.J.
Well my husband and I went throught the same thing and you just need to take a minute to just sit down and let him do the talking. Believe it or not he will be able to tell you in his own way what he wants. Take him to Wal-Mart, KB toys, Toys R Us and let him play with what he would like. Then you should get him those and similar toys. Also plenty of books and puzzle toys, if you want them to last all year long. The more you feed his brain the more it will develop. As for the party... What does he like. My son became in love with Finding Nemo about a month and a half before his 1st and he also loves the water, swimming, taking a bath, ect. So my husband and I threw him an underwater/Nemo party. We had a kiddy pool and a slip-n-slide and a sprinkler. Then for the adult kids we had water balloons (His birthday is June 4th) and then my husband cooked ribs, hamburgers and hot dogs on the grill and everyone had such a wonderful time. Listen to your son and the ideas will start flowing.
Good luck,
N. J
P.S. If you still need ideas send me a message and tell me what he likes and I will give you ideas on what to do.