V.W.
If they are having a difficult time with them or are uninterested, maybe you should wait and do something more traditional for their ages...
Books, blocks, puzzles, games, ride on type toys, paint, etc?
I can assure you, there are plenty of Christmases for electronics down the road. My youngest isn't even a teen yet (she's 11) and I am almost out of electronics to buy. She wants a Nook this year, even though we already have 2 Kindles in the house. She has an ipod (touch) and a laptop. Has had a DS for several years now. Wii, PS3. About the only thing left is a cell phone. And we are waiting on that as Loooooong as we can.