Four grand, that should be plenty for a week of fishing with your son. You said guided experience, and not much else, so type of fishing, and where you sleep each night, not to mention travel times seem pretty much up in the air.

Option #1
Fly out west, rent an RV, have local guides pick you up row you down the river drop you off at your riverside camp each day=trout fishing

Option #2
Drive to the coast, stay in motels, have your guides meet you at the marina/dock fish for whatever they tell you is biting that day

Option #3
Pick a famous fishery, Lake St. Clair, some lake in Mexico, KY or Barkley, the Colorado river; Find a guide service, let them know that you want to try and learn it in a weeks time.

Option #4
Ask you son what you guys could do together that would be awesome. If it were me I would want to fish every day, but unless you are packing into the back country, fishing only might eliminate a hike or horse packing trip. With four grand to burn maybe you could mix in a gator hunt or something, but if you want this to be the best trip ever, plan it together