One of the biggest problems with singing is that as you sing you are setting up vibration in your skull and when your ears are blocked this makes your own voice sound overpowering. Rather like trying to sing with your fingers in both ears.
If you only have a mild loss, I’d consider open fit aids. These block your ears as little as possible.
The best in class is currently the Starkey Zōn. So I’d take a test drive with a set and see how it works. You could have a ‘music’ program set up which may further help with this situation. All that said, hearing well in a singing environment is probably one of the hardest things to do. Hearing aids are all designed with speech recognition in mind, rather than singing.
http://www.starkeypro.com/public/products_solutions/hearing_aid_devices/zon_series/index.jsp
