According to these sources, gophers can bite and can carry disease (as well as other pests such as lice and fleas).
I would discuss any related concerns you have about the children's safety with the school's principal as soon as possible.
Also, if the school or district doesn't have a grounds maintenance crew to address this problem, you might also bring it to the attention of the PTA president. At my daughter's previous school, the PTA president would organize parents to fill in any gaps with groundskeeping, such as weeding on weekends, when the school or district didn't have resources to meet the need themselves.
I'm including below some additional resources you may also find relevant or helpful.