It could be a bit risky to have the Doctor talk to her parents, I guess it depends on timing. It was already risky to know her father knows. It's not really the same with Rose since his death (ending changed slightly, still happened) pretty much erased him remembering ever having met her from the future so there was no way for her mother or even Mickey to know who she really was. I think. I just don't know what you want Summer and her parents to do, do you want them to have one last chat after the proposal and leave or...?