Look at the various options at Newent.
Memory Map on Windows works very well, OS maps on crApple rely on internet connectivity (the ones I've seen). But Win 6.5 is dead, Win7 not out, and not backwards compat. 2 reasons I gave up with Windows Mobile - 1) HTC are about only manufacturers, 2) dead technology.
Symbian is a has been, too expensive for OEMs to implement. Doubt it will be mainstream for much longer.
Android is fast going the same ay as Symbian, according to analysts, Google currently publically stating they will not change their OEM agreements. Has potential if they could get a decent OEM behind it, as HTC have lost their way. Later versions don't work well with current OOF, due to browser bug. There are alternate browsers though.
Gooseberry, only any good for corporates, individuals should avoid like the plague.
crApple. It does exactly what it says. Perfectly. Accept for 2 mojor bombshells:
1) Signal strength for phone is abysmally bad in weak areas. I can not emphasize that enough.
2) Its Apple, and Apple are 10,000,000 times worse than Microsoft for wanting to rule your life, and enforcing their way upon you.
3) Gay
You are welcome to have a play with a gayPhone at Newent. Your son has recent Android to play with, no other choices really....