We don’t fly out that early, but we do Precheck & are usually thru the whole screening in less than 15 minutes. I agree with PP tho, your bigger issue is going to be baggage check. We were there in early afternoon in late January. The baggage check line went straight across the building as far as we could see. We had business select tickets so had a separate check in desk across the hall & took about 10 minutes. The regular check in had that long line to tag your bags, then a separate line for bag drop off. It was crazy & we were thrilled we didn’t have to wait in those. My family members said the line was similar in December & took about 20-30 minutes to tag & drop their bags. I never do curbside checkin. There was a line outside but not near as long as inside. Not sure if that will be easier or quicker for you.
An 8:10 departure will start boarding at about 7:40 -45. I’m not familiar with that car service. If they get there right at 6, figure a few minutes to load your bags & get your kids situated. Are they little? Need to adjust or install car seats? Then 25 minutes to MCO, get there about 6:35? Figure minimum 20 minutes for baggage check, 15 for security. Absolute best case scenario has you thru security at 7:10. Then tram & walk to gait. 7:15-20. Rest room stop & you’re at your gate at 7:25-30. That would be too close for my comfort. If your car is late or baggage or security check takes longer, you could be at gate after boarding already started. Especially if the kids are little & need longer walking & getting thru security.