So the cast should not have taken time out of their day to visit some sick children because a few forum posters online were going to question their motives for no real reason? I'm sure it really brightened the kids' day and like someone said earlier, that's what's important.
They can do whatever they want. Motives and intentions are questioned all the time especially when money is potentially involved, this is nothing new.
Try calling a local hospital about setting up an event and see if you get away with no questions asked about your motives before they allow you on site.
I'm actually surprised some posters here have a problem a little cynicism. This isn't a perfect world after all.
Just because some people are a little cynical, it doesn't make them sick child-eating demons that you get to slay on an internet forum.