My, what violent children your friends have! I looked around and cannot find just a plain slot loading cdrom drive unless it is a exteral pcmcia. Pioneer makes a dvd drive that is slot load but it is about $90. Instead of spending that kind of money why not just teach you kids that computers are not toys and that the weath of knowlege provided by computers will be taken away from them if they treat them like one? I am not trying to tell you how to raise you kids, but, as I am sure you know, computer equiptment isn't cheap, and neither is repairing them.
I have been around computers since I was a fetus, and have never broken or even seen a tray loading cdrom drive broken. Also in my experiance, slot loading drives suck ie:imac's. They tend to have a mind of there own...I like knowing that I can press a button and my cd will come out, not depending on the system to "give up the disk".
Just my random thoughts on the issue. I will continue to look for a slotloading cd-rom drive. If I find one I will let you know.
I would agree that you probably need to advise the children on handling the tray.
I've had a Pioneer slot loader for over a year (fairly heavy use as a DVD and CD-Rom). While it's cool in one small aspect (it was either this or a Toshiba model for SCSI DVD), and it hasn't failed on me in any way nor has ever refused to give my disc back. It is finiky in terms of the insertion of discs. If the disc isn't inserted parallel with the drive or if the disc hangs on something after the catching mechanism has grasped the disc and the retracting mechanism pulls it in, instead of letting go of the disc you hear a transmission like gear grinding sound. This doesn't happen often. It might of happend 5-6 times since I've had it. Most the time I'm able to just touch the disc and the retracting mechanism will pull it the rest of the way in. One time (hmm the last time) I wasn't able to fix it so easily and I believe I had to pull the disc from the catching mechanism.. The gear grinds haven't seem to hurt it but I'm sure continual reptition would eventually cause a gear tooth to break or burn the little motor. Now again as horrific as this sounds, it's only happened a few number of times.. and I don't fault the drive as the first few times it happened were early on because I was not aware of the sensitivity of how you insert the disc. (Slowly and carefully).. Slowly and carefully.. are two things I don't think lend this drive very well for children's use. You might prevent a tray from being broken but you still might end up with another destroyed drive and maybe some CDs as well.
I don't know how they are breakign the trays off unless they are manually pushing the tray in for retraction. If so, teach em to use the button for retracting the tray, which is probably better for the drive anyways. I too know of no CD-Rom only slot drives.. only DVD and expensive CD changers.