M.P.
I agree with Mrslavallie. A better response would be to protect your money instead of banning all children. Having access to money can be a big temptation. I've never had money stolen but I do not leave my wallet accessible when children are around. I've seen reported thefts turn out to be kids not understanding the value of money while iimpulsively taking it. At this young age it's important to teach honesty rather than punish theft.
In reality any one of those children individually or together could have taken the money impulsively. These children are quite young. Taking it could've been done on a lark. I suggest that coming down hard on all of them will make it less likely for them to 'fess up. These are not experienced thieves. They're testing a world new to them. Kindness is more likely to help them tell the truth. Even as a police officer I found it helpful to start an interview having an attitude of expecting the best from the person.