That's a good idea but most of the trusted casinos out there provide really less returns like 1-3% a year as far as I have heard. It may be more but unfortunately it is still less than the return bitcoin provides you every year.
So I would recommend you to not invest in any caaino and let the bitcoin stay in your wallet.
1-3% in a year? where did you heard that? that return is when you deposited your money in bank. I've said if my investment increased 20% since i invested my money in a dice site (if you read my history post, you will know where i invested) on 6 months ago. The return could be more if someone lost a lot or it could decreased when someone won a lot.