Hello; While the inertia of a large mass is likely to help keep it stable and a heavy tank should not easily tip over, the porblem can be that the center of gravity is very high. Most of the weight is in the tank and water high on the stand. I take considerable care to level a stand and tank prior to filling. I also like to use solid shims, usually metal, when leveling a tank.
Some stands have a lower shelf. I often place a tank on that shelf. This adds weight down low and may help lower the cenrer of gravity. I do not have small children around and do not take the extra precautions that I would if they were going to be present.