It sounds like you have a family of foxes. The young will likely move to other areas this fall. But the pair of adults are likely to stick around. There are a couple different options. First would be to bother the foxes anytime you see them in the yard. Go out and yell at them to go away, bang pots and pans, toss rocks in their direction (but not aiming to make contact with them), or use a garden hose to spray water at them. Anything that sends the message that they are not welcome in the yard (without causing them harm). Because they are probably coming into the yard at night, it's important to check to see if there are holes under the fence that they are using to gain access to the yard and patch those (though they can jump fairly high, so it is possible they are just jumping over the fence). If keeping them out of the yard is not effective, the final solution would be to hire a Nuisance Wildlife Control Operator to trap and remove the foxes. They will euthanize the foxes once they are caught. The foxes are very unlikely to go after the children. Kids should be reminded to stay away from areas where the foxes tend to be, if they see a fox, do not run away, just slowly back away and call for an adult.