Ethical questions for teens

i am able o give 1st hand insight into this.. my daughter and her friends were playing at the playground this past holiday.. they found a small change purse w/ almost $1oo $$ in it.. they brought it back to the house and asked me to call the police dept.. i did.. also when they got back to school they were telling the officer on duty about finding it.. my daughter and her friend followed up on it.. yesterday the rightful owner of the change purse was able to pick up her lost purse.. my daughter and her friend refused the $20 reward the lady wanted to give them.. these 2 girls are 12 years old..