Do you think that's enough? He just wants to surf the net and send/recieve email.
'98 is plenty enough for that. Teach him to clean out the cache every so often and to scandisk and defrag, get the security updates, and coach him about spyware and certain hijacker sites, etc, and he should do just fine. (All I'm running is an 800mhz Celeron, for what it's worth, and I do more than surf).
If he sticks with it, and ever decided to expand his horizons, then consider spending for 2000.
My 2 cents....
One thing you can do to save him some boot time and possible aggravation...
Win2k is a networking OS. As such it is set up to use logins and passwords.
When you get him all set up, go into the Control Panel and double click on Users and Passwords. Set yourself up as an Administrator as part of the Administrators Group. Just in case you need to do some Admin work on his box some day.
Once you've done this then click on his username and uncheck the box that says "Use login and password" or something like that.
This will take away the login function at boot up which can be a pain in the ass for a home user.
I set my wife's laptop up with Win2k just because it is so stable and the poor dear has too many other things to worry about during the day. She doesn't need her laptop going all ferklempt when all she wants to do is play some Scrabble.
Good luck!