Running Win 98 huh?
Well, if your grandparents or whoever can get the hang of spyware, anti-virus software and all the rest, I'm sure they'll be able to handle a simple password to get on the network - especially if you name it something easily remembered.
Seriously though, sharing your connection with
anyone could get you in
every kind of trouble. If he's a kid, how do you know what else he might be using the connection for? Porn, illegally sharing files? This kind of stuff could easily get
you in trouble too!
If you want to be generous, just keep broadcasting your network name, and use
this (perhaps - not tried myself) to tell them to come over, you can meet them, and if they seem OK you can allow their MAC address.
Personally, I have my system locked down - I have to enable MAC addresses and have a 26 character long HEX key.
When a friend comes over it takes around 2 minutes to get them on the network - not a problem.
I also use a ADSL moden/router/switch
(all in one), so if I wanted, I could just plug the PC/Mac into the back of it, and there is no need for passwords or anything (I assume if the PC can be plugged into the back of the router, I already trust the user!) This is how I connect up my xbox and main computer (as the ethernet is also a lot faster than wireless).
Perhaps a bit of hardware like this will solve your problems - and it only costs what you're paying for 1 month!