If I barbeque chichen on a (charcoal) grill, can I change the aluminum grill, and then use the same same coals to barbeque vegetables to be eaten with dairy? Or do I need to light new coals to barbeque ’dairy’? Toda!

The coals don't need to be changed. However, I would suggest fanning the coals and making a flame first so thet if there is any gravy on them, it will be burnt and there will be no danger of it splattering on the vegetables.