J.C.
I got my older son a used Gameboy for $25 from Game Stop for his birthday, and some used games. The Gameboy games will work on the DS when he upgrades someday. I wanted to make sure he would get use out of it and be able to take care of it before investing in the pricier item.
Leapster is also nice and I saw some excellent prices this year. My younger son has one - the graphics are excellent, a very nicely designed game. But I don't think the games available will appeal for as long as your daughter gets older.