I agree, put your sons health first. Keep as much carpeting out of the house as possible. IF your husband insists, get a very short loop type of carpeting.
But your son is going to spend a lot of time in the living room, so point this out to your husband. I promise 1 stay in the hospital because of pneumonia, and you will be ripping it out.
Speak with the flooring people about carpeting. See what ther suggest.
We also purchased an electric air filter for our daughters bedroom, of court
Se also no drapes in there. Anything that collects dust and is hard to keep Caen, does not need to be where your son will be spending the most time.