I have never parked at the resort and I'm not sure what they are doing now, but I think they will scan magic bands or ask for name/reservation number to check it you are staying there or have a dinner reservation. But as far as I know, they don't restrict access. Valet parking is also an option at the resort. So, my answer to your question is that I think they should be able to park at the resort.
Magic bands are scanned for everyone trying to access Stormalong Bay. You shouldn't have a problem if go to one of the 3 quiet pools at the resort. Also, there is a very cute kiddie pool and slide behind the stairs that lead up to the Jib Slide- check out Post 3 for pictures. Does anyone know if anyone checks Magic Band access here?
No playground at the resort. I think the closest one is at either the Swan or Dolphin.