When my husband had to go into a care home I was really worried how he would cope without our lovely border collie - he never ever forgot her name, even though at times he didn't know me, and when he was sundowning he aways tried to take her with him. I made sure the home accepted dog visits and take her nearly every time I go, but I also got a life size toy border collie which I found on Amazon - very life-like.
It really comforted him and he carried it about everywhere at first - I told him it was a toy one for him to cuddle when the real one had to go out - but sometimes he thought it was real and tried to feed it. The staff said it was easier for him to settle in bed when they said the dog would be with him and its often by his chair or sitting beside him so he can stroke it
I know your situation is different as your husband is still at home, but its a thought if he really misses the constant presence of a dog, but your son's spaniel and the cats might be enough.
You are so brave to give up your lovely dog in his best interests. I'm sure it will work out. My heart goes out to you and I'm sending you big hugs xx