There is no requirement to break them up, unless they ask for it. If they say they are a flight, then tell the leader who to follow, and clear them to land. As a flight, they aren't all talking to you, only the leader is. Remember, as a flight, they are treated as one really long aircraft. You have to protect the leader and the tail end charlie. When they land, just because you are only talking to the leader, and he's clear of the runway, the tail ender may still be on final. You must protect for the entire flight.
If they are a flight, more than likely they know what an overhead is. However, I wouldn't clear them for one unless they specifically asked for it. Even then, they are still a flight, and one clearance works for all of them.
Now, if they wanted to break up, the current workload and their position would determine if I gave the clearances away from the airport or on the overhead. I've done both; each has it's benefits. It all depends on the actual situation at the time.