Why go to the bother of finding out your rights before even speaking to the company? Surely we are all still able to trust that most companies want to treat their clients well in order to keep custom? If the outcome wasn't as you'd expect, then you could go seeking your rights.
I've never dealt with a large company (which a toy fundraiser would be) that would expect you to pay to return items to them. These companies all have Reply Paid mail addresses. They make fortunes from these fundraisers, they want to keep customers! I've had whole orders for people replaced when they've disappeared without question.
Most often people are so impressed with honesty (which is a sad representation of how much dishonesty they deal with) that they will do whatever they need to, to help out. I've had companies let us keep extra products before.
The OP was about ethics - it asked do I legally have to tell them.....that's an ethical question imo.
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