The only lettuce bunnies should NOT have is iceberg. It has too much water and no nutirents in it. They can have all the hay they want and likewise with romaine and leaf lettuces as well as Boston and endive.
I think HRS has a list of good bun veggies and I think the Rabbits USA recent edition had this info as well.
LIMIT the amount of broccoli they get to one stalk between the two of them once or twice a week.....too much will cause gas which is quite painful.