Hold out for christmas. Don't just buy your offspring video games for no reason. Lol.
Let me break it down for you:
1) Xbox as I see it is mostly multiplayer oriented, whereas the playstation is more single player. However playstation has better games imho.
2) Xbox has 4 controller ports(more multiplayer games). Ps2 has 2.
3) Xbox has better online capabilities via xbox live(although you need a DSL or Cable hookup).
4) You can buy ps2 and original xbox consoles for around 100 bucks apiece.
5) There are a wealth of games for each. Xbox has better graphics but the games tend to have less of a fun factor to them than the ps2. That is a personal opinion.
6) what types of games do they like? Sports games(xbox), RPGs(ps2), Fighters(either- I prefer xbox), Racing games(either- I prefer ps2), First Person Shooters(deffinately xbox).
7) Xbox controlls are bulky and hard to manage sometimes in comparison with ps2. They do work better in some sitations. First person shooters just work so much better with xbox.
8) New consoles will be out soon. Xbox 360 will be out this holiday season. Ps3 won't be out until summer or holiday '06. From all the screenshots and movie trailers I have seen for each system, the ps3 seems to have better graphics and games. The xbox 360 looks like a bunch of stuff they should be doing with the current xbox. I still believe xbox 360 will have a better multiplayer/online lineup.
Really, figure out what budget you want to place first. If its not much go for a current console. You can then buy games on ebay for 1/2-1/3 the price.
Current console = $100.
Old games $20-40.
New console = $300-400.
New games $50-60.
If you want something top of the line wait for the next gen systems.
Sencondly figure out which games you expect to play most and with how many players. Lastly, do you expect to play games online?