Rob- We're new to this and we're not. I raced back in the 80's and then again in the early 90's, so I'm not new to it but I"ve been out of it for a while. At least initially they aren't going to actually race, they're going to run SCCA Solo events in Formula Jr. SInce they are 14 yrs old, they will be running a full size kart with the min weight of 290 or 295 lbs., I can't remember which off the top of my head.
4cylinder - I agree that bullets or wheel weights would likely be the cheapest, but I need this stuff fast and don't have time to go around looking for someone who wants to get rid of it, so it's not a great option for me at this time.