agreed with all ... Also you said it yourself that your parents aren't the fastest walkers out there. The hallways at CGK tend to be long!!! I have yet to find a short hallway from the jet bridge to the immigration/transfer desk.

Also has one said, if they have a checked luggage, there's no way to retrieve it and re-check-in in less than the amount of time they have.

If I were you, have them layover in CGK ! There's a decent Sheraton nearby the airport. This way they don't have to stress up trying to catch their connecting flight.