Isn't better put anything else to eat for them? Ants are do destriyer for some plants or seeds, but also usefull for other aspects: I kill doriphoras and they pick up their bodies for winter storaging, or they keep soft the ground with their galleries. These only for examples. I think it's right to reach a correct balance between us with our presence and the microrganisms from nature. If you may reach this light balance, I believe that your ants will be usefull for your garden. And their observation is very costructive, above all for childrend.