I posted this about 3 years ago, it it wasn't answered. So I'm trying again. It is NOT the adventures of Timothy pilgrim.
This movie was probably made in the 70's, but I saw it one day on nickelodeon in the early 90's. Some kids are helping their parents clean out their attic because I think the bank is going to foreclose on the house. They find a picture of a distant cousin, and the father tells the kids a story about him dying at sea or something. I don't recall the specific events, but somehow the kids travel back in time via some kind of chest in the attic. They travel back to when that distant cousin was alive. He befriends the kids and introduces them to his family (their great-great grandparents). One particular scene I recall is when the kids first arrive back in time and meet their cousin, the boy says he could really go for a cheeseburger, which the cousin has no idea what that is. Another is one where the kids are trying to get back home with the chest. The cousin finds them; the kids pretend they are playing hide-and-seek. The cousin gets mad at them thinking they were snooping around. Around the end, the cousin is about to go on his fateful sea trip, and the kids warn him about the dangers of it. He promises to send them money when he returns. The kids transport back to their time and their father tells them it's time to go. The daughter starts protesting, father tries to pull her out of the chest, and she happens to find a hidden compartment in the chest. It was the money the distant relative sent. The family ends up saving the house. I think the father talks about going to the bank and cashing the check because it was long overdue.