You want your toughest units landing first, along with a Scout Bike Squadron or two immediately afterwards.
The toughest units are there to hold off the initial "mass wave attack" the AI always sends.
The Scout Bikes you send in, one at a time, as fast as possible, straight into their base. Find their main production buildings, and send your Bombing Run there immediately.
Voila, no more respawning Rebs.
"we have an agenda, a character assassination agenda, assassinating characters is what we do for a living" - Sukkit