We did big pieces of 66 from Chicago to AZ in 2012.
Road Trip USA was a help in finding some of the attractions along the way.
Alot of the old road does not exist and you will find yourself on the interstate, I-40, so look for websites to give you info on where to get off. Search Galena, KS and you can find Mater from Cars. There are many other small attractions that are not worth a separate trip but worth driving past on your way. Makes a nice photo op.
I remember that a piece of Rt 66 was on the north side of I-40 in the Painted Desert and you won't find it unless you drove the roads through the desert and forest. They had car parts at one spot and looking along the telephone lines you could see where the road was but not from any other angle.
This happens in many, many of the areas. Don't expect to drive 66 for very long at any one time as it really does not exist in that aspect. It is is most of the small towns and is preserved partially but not like it was.
Two weeks for the trip there and back, LA to Chicago, might be a little quick unless you plan to just drive back straight through.
On edit:
Another link that will give info on the old road is here. You should to a Google search 'Route 66 attractions' for many other sites to help you find the old road.
This one also
