Over helpful neighbours

They sound marvellous. However, I see your predicament. Take a step back. Let your husband go if and when he wants to. Explain that you haven’t the energy but go when you feel up to it. Go for a short while. Just be as truthful as you can without offending. Twice a week visits sound reasonable and lovely for the little boy. Maybe you could suggest they come half an hour earlier so you can chat before you have to start cooking? Or suggest that certain days are too tiring for you? They are clearly kind people who just don’t know what it’s like to be older with less energy.
I hope you come up with some solutions to keep this lovely relationship satisfactory for everyone.

No, not ungrateful, realistic. It’s hard to manage good intentions sometimes and of course you don’t want to offend them. Good neighbours can be hard to come by.

Not sure what I’d do, the only thing I can think of is gentle honesty before I got to screaming point. Do they have parents/grandparents? I wonder if you’re actually filling a space in their lives. So perhaps invite them at a time to suit you, just for a cuppa nothing more and gently explain that although you appreciate their kindness your health means you often need to be quiet and rest. It’s complicated by the fact your husband is enjoying their company, but again explain he has more stamina and so if it’s OK with them he may come alone sometimes but please will they not be offended if either or both of you say you can’t make a visit to their home. Explain about the timing of the evening visits, perhaps suggest a better day/time, just once a week which suits you better. If you stress that you appreciate their kindness I would hope they will understand. Sorry, that all feels like it needs energy to tackle, I’m sure others will have better suggestions.

Next time they come round just on suppertime, say hello, give the boy a big hug and the father a big smile, and say - "Look, I am a bit busy right now, so you two go and see [husbands's name] " Then shut the kitchen door and let husband get on with it. Ignore whatever is going on outside the kitchen - it is up to your husband to police the boy and chat to the father.

Prime husband beforehand that he will be the host if this happens, and it is up to him to see that the boy is occupied and not getting into everything.

That sounds easy Alexa.
Yes, I can refuse the invitations, I do --- but my husband accepts and enjoys the company. I'm just too weak and tired to argue, you need to be feeling on top form to be strong and determined. I just don't know how to stop the father bringing his little boy to see me bang on supper-making time when all I want is some peace.
Yes, I know, I'm an ungrateful cow!

Just say no .