DS is almost 4, his b-day is right after Christmas, and like your DD, he wants for nothing thanks to very generous family. I'm making him or getting him (depends how I feel this weekend) a big brother shirt he can where to the hospital to meet DS2.
What DS1 really needs is time with DH or me, or the both of us, without DS2. Each month, DH or I will have a special activity/fun day with him. In March, we have tickets to go see Yo Gabba Gabba, and DS2 will stay home with a sitter. Maybe one month DS and I go to Pump It Up together or DH and DS go to the zoo together. Stuff like that.