I would wait to see what happens and then, if he does pass, ask the SIL.
It could go either way. I was never too upset to see other babies. Yes, there were very difficult moments, but for the most part, I was grateful to see that there were other healthy babies out there. However, some people find this very, very difficult and I would try to honor their requests if that's the case.
Is there someone that could travel with you and keep your dc at a hotel for an hour or two? Or could you and dh take turns with your dc in the car or something?