Child Damage Mitigation

The famous Bose 901s were either set on a "tulip" stand
or suspended by chains from the ceiling.
I think you can see which method would work best
for your situation.
Enjoy you new gift. 
Stereo gear won't be a priority for next 18 years or so.

In a little different approach, I feel the kids should be allowed to touch all the things with some directions, if possible. However, and that is why bottom-heavy large-base speakers were my recommendation, it may be unavoidable that a child bumps into something while growing up so that particular thing may need to be set up safely.

+1 pictaker5 
perfect solutions indeed 

For those of you suggesting stand-mounts - be careful there as well. My 3  year old son was able to poke a hole in the tweeter of a nice pair of Mission Speakers with a pencil. How or why I will never know . A replacement tweeter was in the cards and an easy fix. the same son enjoys those same towers now in his house 27 years later powered by Rotel . Built like a tank. 

Now the other son found a way to use a small rock to scratch the paint on a near concours 74 Alfa GTV that was in the garage . It wasn't as easy a fix and I surely  didn't forgive him for quite some time. AND no he doesn't have the car in HIS garage :)  !

Good Luck , nothing more rewarding than raising kids. 

Speakers you have heard advice on. If your amp or preamp allows you to limit the volume, you may want to keep that in mind. My boys are teens and I still limit the max volume. 

I’d just nail some chicken wire to the walls and to a wooden frame too high for the rugrats to climb and screen off all the equipment that way, get a remote line-level volume control if your amp does not already have one, and you’re all set. Not pretty but the kids are gonna make a mess of the place for the next few years anyway, so who cares?