Make it only the LVT4, then the LVT2 troop carrier can nestle in with the trio....
Or only one of the LVT2 will have troops while the other two will be a distraction and MG's slaved to the manned troop carrying leader when he fires. If your troop carrying LVT2 dies being the only one that can be manned, the AI survivors keep going as a distraction and stop moving when they hit the beach. Then when you re-spawn to try again, the illusion of a large initiative spreads out before the defenders. You can be given multiple attempts as a trio but, some capped limit of times if you still have AI on the beach and water. Then only the single LVT2 with troops.
Then if you survive and drive to the maproom, your two AI just follow you with MG slaved to yours. If you die, they stop and become distraction targets.