Can I use school aftercare for my kindergarten and 3rd grade daughters for dependent child care?

Yes.

After school care for children under 13 generally qualifies for the child and dependent care credit.

See the following from IRS Publication 503:

Education.    Expenses for a child in nursery school, preschool, or similar programs for children below the level of kindergarten are expenses for care.

  Expenses to attend kindergarten or a higher grade aren't expenses for care. Don't use these expenses to figure your credit.

  However, expenses for before- or after-school care of a child in kindergarten or a higher grade may be expenses for care.

  Summer school and tutoring programs aren't for care.