Great town outside of CDG?

it's a 2 hour drive to the airport from Auxerre, so I suggest doing this:

1. Review your itinerary
2. Identify the place at which you'd most like to have another day
3. Add a day there, adjusting the subsequent parts of your trip by a day
4. Depart Auxerre on Sunday no later than 8:30 AM

Senlis is a beautiiful little medieval town near CDG -- would make a nice day. Be sure you give yourself plenty of time to drive to the airport and return the car.

I'd highly recommend Senlis. It's a beautiful town, and about a 20 minute drive to the airport. We've stayed there several times the night before flying out of CDG. I can't imagine any other option. We stayed in Plailly twice, which is as close or closer to CDG. It has one very good restaurant, but the only hotel closed a few years ago. And it's just a suburban village..

A great town outside of CDG = Paris.

How is it possible to overlook Paris? :)

The OP will already have spent time in Paris at the beginning of the trip.
- Senlis is very cute and close to CDG. But you have to drive all the way past the Paris metro area, and past CDG itself, to get there from Auxerre.
- Fontainebleau is a bit further (90 minute drive, maybe 2 hours at worst if unlucky with traffic), but still good for a 3pm flight and the Château there is incredible. The town is attractive, too.
- An early start from Auxerre will get you to CDG in time, but I understand if you don't want to take the risk! I would be hesitant too.

Thank you all! We will have spent several days in Paris at the beginning of our trip.

Adam & Balso - I took your advice and adjusted our time in Auxerre and Beaune. We were originally skipping Beaune but really wanted to spend time in the Côte d'Or so we added two days there. We will now be driving to CDG from Beaune (3 hours) on Sunday to catch a 3 p.m. flight back to the states. We'll just leave Beaune by 7:30 a.m. at the latest - a little nerve wracking but hopefully worth it!

Hadn't caught on the fact that it's a Sunday. This is in your favor.
On a Sunday morning, the risk of bad traffic is 0.01% (basically, only if there's a bad accident), so driving from Beaune, while a tad long (more 3.5 hrs than 3), is sound.
Do your research on location of petrol stations near the airport, or if available you can pre-purchase the option not to refuel as you pick up the car (it will be one less thing to worry about, and it's not that expensive if pre-purchased).