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.
Gambling sites offer good return compared to banks if you have a good amount of capital, you can double your money in a year and that is fact. When planning to invest in a gambling site, make sure you are into long term investment as the output cannot be felt in a short team. Casinos does not win on daily basis but they do win in the long run, think of that reality and you shall be convince and more confident with risky bigger.