How to protect turntable from children?

Depends a lot on your kids. It's a bit presumptuous for some to suggest that the issue is always parenting. There are limits to how far "parenting" will go -- especially if you have kids with any issues or special needs.

My solution (for now) -- no turntable. Seriously, I can't believe some of the stuff my kids have broken. And they are well supervised and well parented (IMHO).

Dekay's suggestion about the furniture grade media armoires is a good one. I bought a huge (5' wide by 6' high, solid cherry one w 4 large drawers below, a series of selves on one side behind a door and a pair of pocket doors on the other side for about 30 cents on the dollar a couple of years ago. Now I expect it would be 20 cents on the dollar.

You can pick up some of those dog shock collars and put them on each kid. You can also us scat mats and charge them up with, say, 10 volts at a half an amp. That should do it.

Put it in a locked room.

It's called the wrath of dad. Seriously, I taught my kids early on you don't touch moms stuff or dads stuff without permission. Besides these days the are far more interested in their MacBook pros, iPods, iPhones, etc.

My older one is asking for a TT, likely will get a ProJect, or an old Dual and make sure it's fitted with a cartridge where the stylus is user replaceable.