Hi, I just registered but I've been lurking for a while... In regards to your question, you're asking for a three-bike rack that can mount on your rear tire carrier or thereabouts, and you're telling us that two of the bikes have training wheels, correct? If this is the case, you may just wish to remove the training wheels before mounting the bikes, and reinstall them. If I remember correctly, all you need is a ratchet or wrench to get the job done, and that'll save you time and expense in tracking down a specialized bike rack. As far as a 3-bike rack, try and find one that mounts to the hitch receiver. Otherwise, you'll probably end up fabricating something.