Siblings to disabled children

My son was born with a rare heart condition. He will have to go through a lot of life threatening heart surgeries during his life in order to survive. Because of this condition he requires a lot of attention and help, as he's physically limited by his heart. He's one and can't walk because it's too much for his heart. He will be able in the future, but not for now. Before he was born and before we knew about his condition we always wanted several kids and we wanted them close. Now I'm on the fence. Would it be extremely selfish to get more children? The reason I'm wondering is that having more children would mean that only one parent can go with our son to the hospital during surgeries and other treatments, and we're at the hospital a lot and during long periods of time. As our son doesn't have an immune system it means that if his siblings get sick they can't see him, and possibly put him in a very dangerous situation. It would be hard to avoid as the other children will have to go to school and possibly daycare. Our son will spend a lot of time at the "hospital school" since he's so "fragile" and will be spending a lot of time at the hospital. His siblings would also get a lot less attention as we have to help and monitor our son. I know the risks are super small, but if we got another child with any kind of disorder our lives would be impossible. What would you do?