Definitely your house, your rules. No way would I have a child jumping on my furniture, or climbing on the bannister. Not only could they cause damage, but they could potentially cause harm to themselves. If you do go ahead with having them to stay for Christmas, and your grandson starts to act up in any way, I would casually ask your son (if he is present) to tell your GS to stop what he's doing before he damages something, or hurts himself, as it's the last thing you want happening, and it's not acceptable in grandma's house. If your son isn't there to see the behaviour, I would say something like, 'please don't do that, grandma doesn't allow that in her house, because you could damage the ...., or hurt yourself.' It's better, if possible, to allow your son to deal with the situation, otherwise he may feel that you are challenging his parenting skills. And, if he doesn't deal with it, you then need to let him know that you're not happy about it, and it's not something that you allowed him to do in the home when he was a child.
Regarding the bathroom issue, when they arrive, I'd casually point out that you have left a supply of bath/shower spray/bleach, and a cleaning cloth, so he can give the bath/loo a quick once over, after they've used the bathroom each morning, just so you don't have all the extra cleaning to do when they leave, which would be much appreciated. Hopefully, he'll get the message.
Above all, for want of a harmonious Christmas, try to keep your cool. Engage with your grandson as much as possible, playing games, etc., and try to make it a special for him. If dad is often so busy on his phone, maybe your GS's behaviour is an attention seeking thing ...?