While an AC will help, it can only lower the air it intakes by a certain amount of degrees. The larger the unit, the lower the air temp can be made.

The air around the light will be very hot.

Put at least one large fan blowing OUT of the bathroom.

Create negative flow and make sure one fan is blowing on the lights and another fan blows, or rather, pulls the air OUT of the room.

Hot air rises so see what you can come up with.

A more detailed view of your grow room would be helpful...