OK, lets see if adding 4 inches on each side of the speaker 'base' will help prevent tipping... ( I don't think 2" would be sufficient)
Here are my assumptions:
you have M80's with carpet spikes so sliding is not considered
Tipping sideways is considered since it will be easiest to tip that way.
The average 2 yr old boy is 3 ft
(link), so lets assume they are pushing or pulling 2.5 ft off of the ground.
Here are my results:
As is:
A force of 8.99 pounds will be required to tip the speaker when pushing horizontally on to the speaker 2.5 ft from the ground
With an additional 4" of 'base' added to the bottom:
A force of 16.57 pounds will be required to tip the speaker when pushing horizontally on to the speaker 2.5 ft from the ground.
Conclusion:
a base increased by 4" on all four sides will require about 1.8 times the force to push/pull it over.
Next we can calculate the force the speaker must withstand in order to resist tipping due to the momentum of a toddler in full sprint...
do you think a 2 yr old running down the hall and hitting a speaker at full sprint will impact the speaker with a force greater than 16.57 pounds?
I say we need more than a 4" base
perhaps the shock collar isn't such a bad idea after all!
