Lettuce is not good for him, at least not iceberg lettuce, so don't worry about him not liking it. And if you are just giving him a little grass, there's no such thing as a "bad kind" as long as the lawn has not been chemically treated.

For a treat just about every bunny I know loves, buy a bunch of flat parsley in the produce section of your supermarket. It'll cost you less than a dollar, and make him very very happy!