My house has wooden floorboards so I prefer to isolate rather than acoustically couple using spikes. It might be worth you looking at Auralex Propads. I've no experience using the Gaia feet but from a theoretical perspective to achieve optimum decoupling you really need to spread the load across a large surface area (the opposite of spikes).
I need the ability to lock them down so they won’t get knocked over as I have a five year old.This is probably going to be your main issue because as soon as you do that you'll be directly coupled into the floor again... unless you mean lock them down while you're not using them. Another approach could be to see if the sound is improved by standing the speakers and stands on heavy slabs.