There have been significant problems with over-crowding at some of the premier resort hotel pools at WDW, so use of hotel pools is now limited to guests of the specific hotel or complex, only. It is, however, only enforced at the more deluxe, popular or crowded pools. You didn't mention which two resorts you're staying at. If one of your two families are staying at, for example, an All-Star Resort, there is probably no problem with you all swimming together there. I've never read any reports of them checking resort IDs there, though I'd personally ask permission to do so. On the other hand, if one of your families is staying at the Beach Club Resort, then you'll almost surely NOT be able to swim together at Storm-a-Long Bay. Resort ID is checked quite closely and the restrictions on hotel pool use are enforced quite consistently there.