Two-Year-Olds and Turntables...

I have the same problem and solved it by placing a strap or belt around the plinth and cover which I remove when my grandchildren are gone. Works just fine.

Of course, that didn't stop my grandson from tweaking the treble on my C2200. I went through 3 sets of tubes 'cause I didn't like the sound before I discovered that the problem was the treble knob that was cranked to the Max. After living without bass and treble controls for 15 years I completely forgot about it. As my son would say... "Well, Duh!"
OK. OK.. So, Gramps is a slooow learner...

I realize all kids are different, but I was able to teach my son that some areas are a "no."

The "no" areas included things under the kitchen sink (we did not lock the doors), electrical sockets (no hairpins please :^) and my turntable.

By the time he was walking, talking and had a reasonable understanding of things, I showed him how the turntable worked and he would cue up music while I sat in the hot seat. My TT at that time was a Versa Dynamics linear tracker with Benz Ruby cartridge.

I have a Polaroid of him standing beside my expensive gear with a grin from ear to ear. He was laughing out loud when the music burst into the room.

No, he never broke my stylus or TT, he left that for me to do while I was cleaning the body of the cartridge with a Q Tip.

I should have let him clean the stylus.

That is a tricky situation, can you place a chair in front of it so it is hidden behind the chairs' high back?

I took a different approach, which has worked (so far).

We have a 22 month old, and I bought him an old Kenwood direct drive that he can play with all he wants (not plugged in), it's just sitting on the floor in his play space and he has his own little library of records that he can chew, dance on, or spin - it's up to him. He gets excited when I bring him a new record too! Once he's old enough I'll see if the table will still work so he can really use it, but for now, it definitely keeps the heat off mine.

A very none politically correct idea is
It may be your grandchild but it is your offspring's child, hence if they wish to visit and have you be relaxed and enjoy it, it is their responsibility to either pay attention to their child or not stay to long.
A visit is meant to be pleasant not unnerving
Having no grandchildren yet I can say this, when I do I may regret it.