Firstly you have to approach local restaurant owners and find out which nights they are quiet (usually early in the week).
Then suggest that, if you arrange to bring a large number of people on a certain night, they could provide a menu or buffet for a set amount. The lower the cost, the better.
You will have to tell the restaurant approximate numbers – it may be worth asking people before hand to gauge how many would be interested. Then arrange a date (usually a week beforehand) to confirm numbers.
You then sell tickets for the meal at an increased price – this additional amount being donated to Young Heroes.
Maybe you know of a singer, comedian or band who would be willing to donate their evening to the curry night (you would need to obtain permission from the restaurant) to add that little bit of entertainment.
To promote the night you could put leaflets into the restaurants takeaway bags and menus a few weeks ahead and see if your local paper will help promote the night. The restaurant gets more trade than they might usually mid-week and you raise money for Young Heroes.