So, as far as I understand, it is ok to use a partitioned drive for TM, I can use CCC to copy the internal drive on the old computer onto a small partition of the new external drive, and then they will be using the other partition of the new external drive for TM. The old TM drive that went with the old computer is going to hard drive heaven because it is already corrupt anyway. The drive on the old computer is then wiped, a new system installed, and it goes to the kiddies at home. Right?
Correct.
If the point of copying the existing internal drive onto a partition on the new external drive is to make available user data without the complications of migration, you may be able simple to copy rather than clone the data in question. If you want existing apps to be available also, you'll need to clone instead, if any of the apps originally required an installer.
But the process of starting off with a clean slate and adding old material by copying as needed is a perfectly reasonable approach. I've employed it not only for new Macs, but for OS X upgrades as well.
