….to tell Amy & Rory’s parents what happened.
They’re in the past. All they have to do is set aside a will and a box at their lawyer’s with special instructions to be delievered to their family the day after they disappear in 2012 with a long letter, journals, and pictures of their lives in the past.
Yes, it would be hard for their parents, but they would be better off getting proof that their children lived a long, happy, loving life together in the past than to have the Doctor just show up and say “I’m sorry” and leave them forever wondering.
That’s what I’d do with my family if that’s what happened to me.