The Bay Island lie about 30 miles North into the Caribbean off of mainland Honduras. There are many islands, but most folks first consider Roatan and then Utila as the most likely options, following with Guanaja and Cayos Cochinos on down the line in terms of visitor count.
The islands are part of the second longest barrier reef system in the world- shared by Belize which is about 90 miles to the NNW.
The Islas de la Bahia lie just South of an active earthquake epicenter underwater fault line. If you are lucky, you may hear a "snap" while underwater, or see the beer bottles jostle on the table!
On Roatan, you can select from several AI resorts, as well as 15+ major day-dive ops that cater to the divers who stay at the many guest house establishments.
There is one heck of a lot of good info right here on Scubaboard Do some searching and more closely define your questions- beyond the literal answers I gave above.
The best way to begin your search: Specifically define for us your wants and needs. Start off with the age groups you have. Are they a 2 a day group or like more diving? How much night diving do they want? Is shore diving a must-have? Do they like to go out for some partying every night, or do they prefer a night dive and bed?