My .02 worth. OW coming for a 4 day visit. H wanting to do the yard work. Sounds like a whole lot of guilt playing on H's mind. I'd just let it play. Your response about the yardwork should be, No thank you, I have plans. Nothing else. Your H is trying so hard to suck you back in. He wants you right where he left you and it's giving him fits to find out he doesn't have control over you. Don't give your H any clue as to how it's affecting you. Sorry Bubba, you made your choice.
Let his guilt prey on him and put a damper on the ow visit. Hopefully 'Mother of the Year' will have her own guilt to deal with. Maybe they can both drown in their self pity.
You are a kind woman Mila, but don't be afraid to show your strength and confidence. Your H is going to rely on it when he comes through.