We just did this trip in May (well, slightly longer - we live in SE MA right on the RI border). We're veteran long distance travelers. We drive to DE every year to visit MIL and have gone camping to CA and back with the kids in our van. The actual trip time driving time for us was 47 hours round trip. This includes traffic jams.
Some things to remember:
1) If traveling down 95 pack plenty of 1s and 5s in the wallet. As well as a roll of quarters and a roll of dimes. The Tolls are BRUTAL. I think the total Toll cost was around $75 round trip. All the tolls were north of Washington DC. We didn't use the whole roll but the good thing is when you get to WDW any quarters that you haven't used you can use in the Frontier Land Shooting Gallery.
2) Our gas cost was around $275 round trip. The cheapest place to get gas was believe it or not NJ.
3) We actually skipped goody bags for all our trips. We just let them pack a back pack of their favorite things. I did buy them some new books.
4) If traveling at night bring pillows and blankets. As you are leaving at 5 PM stop around 8/8:30 to change into bedtime stuff and brush. Don't put the kids in their jammies before your leave. This makes the transition to bed time more real and the kids more apt to sleep. Even the 10yo should change clothes. Have him bring a pair sweats or sleep pants to change into in the back of the car.
5) I second PP plan stops every couple of hours and bring a container for accidents. I can't tell you how many times we started looking for a rest area and couldn't find one for over half an hour. Even with the container we STILL had an accident. So pack a garbage bag in case there is a wet seat.
6) Even at that time of night travel thru NYC is rough (I've done it more times than I want to think about it). We generally avoid going thru NYC and travel via the Tappan Zee Bridge then Garden State Parkway.
7) A few places the GPS lost its signal usually at critical junctures when leaving tunnels

and a few times tried to steer us wrong when there was major construction underway which changes the exit ramps. So make sure to pack up to date hard copy maps. Make sure to have a navigator available to watch the road signs in high traffic and construction areas as you can otherwise easily end up on the wrong road.
8) In a few places you end up driving right by some major event venues (stadiums/Nascar speedway, etc.) Check before you leave for times for these events so you know to avoid them if possible or to drive by them if nothing is going on (We had to skirt a NASCAR race in Richmond - in this instance it was actually faster to go thru the city instead of around it).
Good Luck!