Question on colonoscopy prep

I’m having my first colonoscopy tomorrow morning. I have to take 2 dulcolax laxative pills at noon today, mix an 8oz bottle of miralax with 64oz Gatorade and drink that from 4-6pm, then wake up at 2:45am to drink the magnesium citrate (there’s a powder packet and the lady said to mix it with 7up). Has anyone done this variant of the prep before? The clinic is almost an hour away and I am not sure if I will still be running to the bathroom when I’m driving there. Is there really anything left in my system after the miralax and Gatorade mixture? What will the magnesium citrate the next morning be like?