When are you getting the bunny. I'm sure your son is thrilled, but all the homework should be done before you bring the bunny home.
Be sure to ask for a small supply of the feed the bunny has been getting because sudden changes in diet, particularly for young bunnies, can easily upset their systems. This goes double when the bunny is already stressed from going to a new home. Get the name of the feed and buy a bag of the same kind, even if you intend to make changes later. All changes should be a gradual transition. I can't stress this enough. Rabbits are very subject to stess and it usually shows itself as a digestive problem. These problems can be fatal.
You need a good general book on raising a pet rabbit. Reading everything you can on the forums is also a good idea. You don't say how old your son is, but it is important that he understands that the rabbit at 6.5 weeks is a baby and cannot play for long periods of time. It needs peace and quiet at first, then gentle petting and as it becomes friendly it will enjoy your son's company and look forward to their times together.
Your bunny needs his basic feed, clean water and something safe to chew on to keep his teeth worn down. A branch of a safe tree is good for this: apple, willow, elm, aspen/poplar or maple are all good. Make sure they have not been sprayed. A piece off an untreated 2x4 also works. If at all possible get some timothy or grass hay for the rabbit. There is nothing more healthy as a dietary supplement than good grass or timothy hay. It helps ward off many problems.
The cage will be fine for starters, but since you don't give its size it is hard to know whether it will be okay when the bunny is full grown. The litter box is likely best filled with those pine pellets or with a product like Yesterday's News. Do not use a clay litter.
Be careful when the bunny is out roaming around. They will chew on things... including furniture and electric cords. Not good! Warn your son to be careful not to step on the rabbit. This is a more common accident than one would think and it makes a person feel terrible if it happens. (I stepped on a baby chick once and still feel awful about it, even though the chick survived.)
Well, that's a start for you. Hope your son enjoys his pet rabbit. The House Rabbit website may be good for you to check out. I do not agree with everything there but it will give you information to condsider.
http://www.rabbit.org/
here is another useful site for understanding a rabbit's body language so you can communicate with it better:
http://language.rabbitspeak.com/
Good luck with the new bunny! :clover: