They can travel in drop ships, but they don't like it. The plan will be to send a troop ship alongside the assault carrier, and load them when ready for the strike.
And you can transfer ground units from ship to ship in the middle of nowhere? Sounds a bit strange.
And it makes my "assault transport" design of a 20k jump capable military ship able to carry three battalions and having hangar space for three 1000 ton assault shuttles, each with a battalion drop ship, a bit of a waste of displacement. Maybe I'll scrap the transport spaces and add hangar space for some gunboats or more assault shuttles.