Help!!!!!!

Ok so I was trying to hack a game so that it would give me free coins and while trying different methods I accidentally bought $100 dollars worth of coins!!!! Now I'm only 13 so this was of course charged to my parents credit card! 😭😭😭 I came clean and told them what happened and they were totally cool about it and said that is I just pay half of it back doing chores then it will be ok and forgotten. This is very generous and understanding of them and I've said thank you like a 1,000 times and I keep saying sorry but I truly want them to know that I'm sorry and that it won't ever happen again. Any ideas on how I can show them that I'm grateful?!?!?