We just bought DD a Nintendo DS for her 9th b-day coming up in a few weeks. She has the SP and loves it but her best friend has the DS and she has been begging and pleading for one for her birthday so that she can play Nintendogs with her friend

I told her no way was I buying her a new DS because she just got the SP for her birthday last year but we are going to surprise her with it - and boy will she be surprised! Her little brother (6) will get her SP. I would splurge and get the DS if you don't mind spending a little extra.
We did the Target deal and got Mario and Luigi - Partners in Time as our free game. The other game choices with this offer were MarioWare and a Kirby game (can't remember the exact title). That's the best deal I have seen and I've been looking awhile.
Good luck!