Originally Posted by
Mike
If you don't have a roll bar, it's better to not have seat belts. If you have a roll bar or cage, then seat belts are preferred.
In your case, the purpose is a little different. You are trying to keep young children from getting thrown out. It's a bit of a trade off in restraint vs rollover protection. Since your children are so young, I doubt you are going to be doing any on-the-edge style riding and in that case I wouldn't see the belts being a big deal without a roll bar or cage. You can bolt seat belts to the frame or to the body. If you choose to use the body, large fender washers will help distribute the load without ripping the HDPE. Cheap car seat belts would work fine and probably allow you enough room to bolt them down to the frame.