I adopted my foster child. There was a grandparent couple in my class. I believe that you will go thru the same process as any prospective adoptive parents.
Whether or not they offer child care depends on the office thru which you're going. Are you currently approved as foster parents? If you're already receiving assistance you will continue to receive assistance. If the children have not been placed with you by the state as foster children I doubt that you will receive assistance. The reason that foster parents receive assistance is that the child(ren) are wards of the state making the state responsible for their welfare. Once the adoption is final you will not receive state assistance.
If you haven't already been assigned an adoption worker you will be soon. That is the best person to answer your questions. Each state may have different rules. If you want to ask questions before you're assigned a worker, call the intake person.
I've seen support groups for grandparents adopting grandchildren. The agency that you are working with may have one. You can also look for info on the Internet and in local neighborhood style newspapers/magazines. You can find them for free at super markets and the library.