Icy Wind can't be used because its multi-hit and wrecks the zeppelin.
It was a very deliberate design choice in this arena, in fact it's the whole point; moves like Rock Slide, Blizzard and to a lesser extent Icy Wind (its fairly weak but still) are pretty broken in multi-battles, especially triples.
Dratini, use Light Screen. If you are Taunted, Dragon Pulse Mind insted. Then, Dragon Pulse Haunter.
Squirtle, Bite Haunter then Brine him.
Dunsparce, Headbutt Mind then Bite him. Or if we're breaking the rules now, just Rock Slide everything twice.