C.W.
The only advice I have is to absolutely have it done in a children's hospital, if it isn't already planned for one. Even if you have to drive a ways to do so.
The children's hospital we use(90 minutes from us) has a separate pediatric section for EVERYTHING, including radiology, apart from the "main" hospital .It was a big difference from using "big people" hospitals, in my experience. When you're with people who only see children, there is much less risk when it comes to things like, say, calculating sedation medications. They're also much better at comforting the little guys!