I'm very bad at guessing age in my own opinion. Then again, it is very difficulty as young people depeding on their life can look much older and vice versa.
I would put them as older, but healthy couple (minus Stan's cancers). I don't really think they would be older than 70 and I think they are more on the 60, so I agree with you that they aren't younger than 50 and not older than 70. Perhaps the better age range would be 55-65, yet I mostly wouldn't be able to hit a Piñata too, so who knows.
