Best stands so baby doesn't knock speaker over

don't do it

I've had many kids and many speakers. Only way is to ensure that kids  can not get to the stands/speakers at all. We used folding gate like things which created a barrier around the speakers which yes are ugly. Out of reach is the only other viable solution I know if if you can put the speakers on a bookcase or piece of furniture until the kids are older. Even with 100lb stands they can still rock them and topple the speakers over on the floor or worse their heads.  

FWIW, we only had to do this for a couple years. Of course there is the tweeter poking issue but that argues for horns. 

Dtx, simple. You get high strength scotch double sided mounting tape, the red stuff. you run three long strips on the bottom of the speaker and three on the bottom of the stand. If you have a carpeted floor run four 3 inch self tapping wood screws into the floor. Drill pilot holes in the base of the stands and run the screws through the carpet into the subflooring. Trust me on this. You will have a very hard time separating the speaker from the stand. A child will never do it. Removing the screws is far easier. You will not leave a visible mark in the carpet. 

My favorite story is my pal that had a nice stereo and a small child. The child pushed open the CD player, put a big handful of oatmeal on the tray, then pushed the close button. That was funnier than watching tweeter domes get pushed in.

Good luck drilling into pile without running it.

My bedroom speaker set is wall mounted on extended brackets.