Thank you for the additional information.
In my mind, I see a "family" who needs to get away, take a vacation, and get away from the stress of what has been going on. You are enduring a lot, right now.
The therapy is good, but sometimes a break even from that is in order.
The problem is, can you afford a get away.
I see you are from California.
But a mountain retreat would be really great for you, your husband and the kids, wouldn't you say?
For example: Something cheap, not too expensive would be say Langhorne Pennsylvania. Santa Barbara would be too expensive.
I do not mean camping. Camping is too much work. Langhorne, PA is a family resort, with golf, swimming pools, a country side to walk in and everything is on the cheap. So it is not a budget buster. BUT you do not want cook, or do anything, so this is a great place.
And there is a beautiful Longwood Gardens near by, a Dupont estate where you can spend a day, and they have a picnic grounds where you can picnic.
An alternative is a family retreat house that most catholic communities or other faith communities have. they sometimes have a place where you and your husband can hang out for a few days.
Now lets talk about the separation you spoke about. I am also concerned about the children. You said you were married 21 years. I do not recommend that you separate unless you are contemplating a divorce. I did not see that in your question.
The reason is, that you are going through a tough time right now and it is stressful. The fact that you came here to ask this question, indicates that you realize there needs to be some decompression. AND, I agree. If one of you getting away for a few weeks is the only way you can mange it without vacation, then perhaps it can take on a form like this:
One child goes with each parent and take separate vacations....I recommend not less than 10 days. 14 would be better. If your work will not let you be gone that long, then take what you can.
Time away that is framed like a separation, is more sever, like trying it out to see if you should remain married or not. I do not see that in your question. What I see is that you need some time away, not necessarily from each other, but just away. So frame it as a vacation. That means there is no pressure to decide if you should be together or not, you are trying to decompress to deal with the stressors.
Another issue is that if your husband is depressed, and you as an observer, probably know that better than he does. It is frequently hard for someone to recognize themselves in depression. The depression could be caused by his feeling guilty as well as the situation you find yourselves in, and that depression in turn is what is most likely affecting the sexuality. It sounds like he has been depressed for a long time. It would not surprise me at all, if the children were also suffering from at least a low level of depression. (it sometimes spills over to the children)
so what is your husband doing about the depression. Depression is treatable by talking to a counselor or even a close friend, and if sever enough, medication.
Yes, I agree that you need time apart, but not as a seperation, call it a vacation. AND If you can, make it a family event, but if you cannot do that, then seperate vacations are appropriate.
Take the children on the vacation with you, if you can. Or this can be the year everyone took seperate vacations. (or the children can stay at grandma's)