J.D.
in the house... playdoh, playing with any type of figures... my girls love barbies or anything they can pretend play with. Since you have a boy... maybe farm figures, or dinosaurs (my girls love those too), other crafts, coloring, etc.
I live in South Jersey... I'm not sure where you are exactly, but there are SO many places to take the kids! check out this link... http://www.funnewjersey.com/
you can go to the zoo, a kids museum, the park, and indoor climbing/jump place. Alot of places your son will be free, or if you have an entertainment book, they have lots of buy one get one free coupons. Since your son is the younger one, I'd say anything he would do, she can do with him. have fun!!!!!