I don't think this visit has anything to do with Tom. It's got Marvel/ Disney usual fingerprints all over it. They've always been big on charity and they send their actors to children's hospitals for movie promotions all the time. Loki and Thor are Marvel properties. They wouldn't be swayed that easily by Tom because he wants some good press. That would mean he's pushing his employer to help him with his own image and Marvel isn't going to arrange this at one actor's behest. This hospital itself is a big celebrity draw so based on Marvel/ Disney's history, I believe this was their idea to draw attention to their movie as well as to give back to the city since they are using the country's funds, and Chris is beloved in his country so it makes sense for him to give back. Its focused on Thor, not Loki. If it was at Tom's request, we'd see him more front and center than Chris.