T.C.
Balloons or balls are great. First birthday parties are more for family and a photo op with baby getting cake and frosting all over himself. They need a short party, not during what would be nap time or meal time. Preferably when he is awake, but well-rested and fed.
Too much and he may become overwhelmed. Presents should be already assembled and loosely wrapped. I actually started a rip in the paper for them.
There was a balloon for each guest and the birthday boy (with extras in case of 'accidents.' A small ball from the dollar tree for each child (about the size of a large grapefruit)
They played with the balls, ate cake, unwrapped and played with the toys and it was all over. Birthday boy gets a quick bath and he is ready to nap.