Hey!
We have three kids 10, 13 and 17 and have had Gameboy since the oldest was 7. Yes, they do make new ones, but usally the old games play for a few years so you don't have to replace one or the other right away. I can say that since our oldest got her first, one has been in nearly constant use at our house since then. They seem to last, and are great tools for us as this is one of the first items we can snactch up when the kids are either misbehaving or not doeing what they should. The DSi has texting and other things that will allow the child to communicate with other people, the DS has a feature that will allow the child to link up and play games over wireless internet, but has fewer internet features.
You should be able to pick up a good, clean, used DS from places like Game Stop at a much cheeper price too, and the used games are a good value and you can also sell games back if the kids don't care for them (keep the packaging to games and this will up what they give you at resale!)
M.