Karma?

Okay so I believe you do to others as you'd like them to you. Last night I had a table that used a coupon card. With those cards we always add the tip (18%) which I did. They had given me cash and I returned the change to them and they got up to leave. When I went to the table to I noticed they had left me $25 . I noticed they were still in the parking lot so I went outside and told them while I appreciated the extra tip I didn't think they realized that an 18% tip had already been added because they used a coupon. The guy thanked me and gave me $5 for my honesty and went on. I believe it was the right thing to do. I mean yeah I could have had 20 extra bucks and if they had not been in the parking lot I would not have felt bad about it but they were so I did the honorable thing. Anyhow most to the staff said I was being a idiot and should have just taken the extra money. What do you think?

Right now I am hoping for the rain to stop. I have the host family conference this afternoon - a picnic in the park. I rented a picnic shelter and so far am out $100 and it doesn't look like the rain is letting off. This sucks because I need at least 10 families to attend to make back the $100. So far only one said they are coming despite the rain.