Devorgilla
I read the OP again. I think the least you should do is get someone in to clean the bathrooms and kitchen prior to your operation and for a period afterwards. I think it would give you some peace of mind. Just close the doors on the other rooms. I see your son who wants to bring the girlfriend doesn't live with you so maybe he can persuade the brothers to tidy their areas. The plastic boxes are an excellent idea. Fill them up, label them and stack them as near to where your husband/sons sit as possible.
This is one of the more helpful responses here. There will be lots of underlying, long run habits and behaviours here. Expecting that asking everyone to change/putting your foot down etc will result in a magical transformation is unrealistic. And we don’t know how angry this husband can get. Or how well OP deals with conflict.
I would start with getting someone in to clean the shared spaces regularly. Focus on neutral areas where no one has ‘ownership’ - kitchen and bathrooms, hallways and stairs. Be calm and clear with your family about what will happen, and the limits to where the person will work. Don’t worry about a deep clean - this is only what a decent cleaner achieves over a few weeks anyway and it doesn’t last!
Use an agency like Maid2Clean (or another). They are more expensive but will find you a cleaner quickly - and if you don’t like them, the agency will find you another, without you having to have the embarrassing conversation. Cleaners see everything - they will have seen loads of cluttered grubby houses and yours will come as no surprise.
Hopefully your family will get used to it in time, and might even like having cleaner, tidier spaces.
I am surprised at people who think that you can simply move or even throw out all of the kit associated with your husband’s hobbies. I am going to guess that they have never dealt with this issue irl. I’m very sympathetic to this which is a problem I share to some extent. I have found that I can sometimes ‘tidy up’ my OH’s stuff. I use plastic boxes and label them to get things a bit more organised. I have to wait until he is out though. He hates me doing it, but I think that sometimes he likes the result.