Are you referring to R&C?
If so, then yes, you can ask your server to hold your table while you go to the R&C reserved area, and then come back to your seats for dessert/drinks while the park empties out. Though, with your ADR time, you might not be done with your entrees yet when Illumination starts.
R&C's last ADR time is 8:00, so you'll be one of the last parties seated. Given that, there won't be any parties waiting for your table when you're done, so there will be no rush to leave your table. The minus is that you'll have to take what you get in terms of table location, as yours will be among the last open tables for the night.