Can they make an MDE account now? It just makes everything so much easier. But, they should be able to pick them up at the front desk when they check-in if not.
If they make an account then they will be able to customize their MagicBands, among other benefits. If they don't then they will be given MagicBands when they check in. Most likely they will get grey bands.
If your parents are unable to figure out how to make a mde account just ask them for there reservation number and you can do it for them. If they don't want to pre book dining or fp that's fine but atleast they have the option.