Don't run AC into the crawlspace. It will pull the main house into a
negative pressure which will suck crawlspace or outside air into the
house. This will reduce performance of the ac and heat serving the
house. It can also backdraht a flue and kill you. Far better to put a
dedicated DEhumidifier in the crawlspace and close the vents after you
put plastic on the ground. To try to condition the crawlspace with the
vents open is like running the ac in your house with the wimdows open.

Stretch