If he has a stash of DDR2 then it makes perfect sense to buy an AM2+ board . . . if he doesn't then I agree may as well go DDR3 . . .Why do you want to stick with DDR2 ram?
Why?If you can stretch to it you would be much better off going for a DDR3 board and new ram.
Try but i was thinking along the lines of scope for future upgrade if he goes for a AM3 MB then it will more than likely be DDr3 then in the future he can upgrade his CPU without having to upgrade the board and ram at the same time.
This is of course just my opinion