I would recommend doing this on Plantation and with at least one person using an M-107 sniper rifle. Shooting from further away increases your survivability and while this map quite a few trees, there are many gaps you can see / shoot through with a sniper rifle. The M-107 can take out ADAT's with just over a full magazine and any vehicle in the convoy with fewer shots. Before you destroy ADAT's 2 & 3, I recommend sniping all rebels near them and the enemies inside the building with the ammo box. Be sure to position yourself so that you can quickly move in and destroy the last ADAT after you've blown up the 2nd one. Note that you do not have to complete the secondary objective of clearing the camps to earn this achievement.