My son goes to a sitter while I’m at work. It’s one on one. She has a three year old son. I want to…

My son goes to a sitter while I’m at work. It’s one on one. She has a three year old son. I want to get him something fun for Christmas that my son can also play with there since I’ll be working more hours due to tax season. What’s a good gift that a three year old and a nine month old(he stands, climbs on the clutch, etc) can enjoy?