L.L.
There are a ton of gifts that can be shared between a 2 and 6 year old. My children are 2 and 7 (almost 8) and they share things all the time.
I have seen some awesome art easels for around $20...I think Aldi's might have one.
A toy shopping cart full of food, or a toy cash register, or a toy food playset. Target has one that comes in a basket with a little cutting board and "knife", and you can really "cut" the food (which is cut in half and held together with velcro.) My kids LOVE this toy.
A board game would be good, if you know they don't have it...my kids do like Hi-Ho Cherry-O, Hungry Hungry Hippos, etc.
Ooh, you know what else they LOVE? Those little battery powered fishing games where you have a little plastic pole and you try to hook a fish as they spin around in a circle opening and closing their mouths. Those cost between 5 and 10 dollars...you could buy one, PLUS extra batteries, and still have money left over for something else. Seriously, that games has lasted a long time for us.