My DS is 6, 7 in a few weeks. We use a family change room at a pool, although they can be hard to get. If a family room is not provided by the facility, I either wrap him up in a towel and he showers/changes at home or I help him to change beneath a towel beside the pool. There is absolutely no way I would allow him to use the male change room unaccompanied.
As for toilets, I take DS to the toilet in the parents room if there is one. If not, I have no hesitation using the disabled toilet. I have told DH to do the same if he is out with DD1, who is 9.

