The work boots may be OK for a while, but when it comes to the kids, you shouldn't take chances. Where he will be riding does play a role, if he is riding woods with you, then he could easily hit a rock or some peice of local plantlife. If he is on an MX track, then the risk of falling and having the bike land on his leg increases. Alpinestars Tech4S run about $105, and there are cheaper MX boots out there. If they are bought a couple of sizes big, they can last a couple of years. Basically, I am for spending as much as you can afford to protect your children in the best way possible. The boots are more important than the pants, pants to provide some abrasion protection, but nothing for impact. The jersey isn't that important at all. Knee and elbow pads, a CP, and neck roll (he won't grow out of these anytime soon) are also more important than the pants and jersey.