For your son, I wouldn't recommend buying the best rod on the market just yet- if he decides to drop fishing, then it wouldn't be good to have thrown a whole bunch of money down the drain. If your son decides to fish more, though, I would then buy a better rod for him so it can be a more enjoyable experience.
As for your size of rod, if your son plans to catch smaller fish species, then I'd elect for a 5-8 lb rod. If he plans to go for larger fish, then I would lean more towards a 10-16 lb rod. As far as length goes, it really doesn't matter all that much in my opinion. A 5 ft rod would be optimal, but you can go up to a 7 ft rod if you can't find anything else. Since your son is new to fishing, it would be best for him to have a push button reel, otherwise it would be difficult for him to learn a full reel with no experience whatsoever (I speak from experience here).
For a kit, I'd buy him some line that has a pretty similar rating to that of your rod and possibly some lower-rated lines as well if you plan to go fishing for smaller fish. You could get some lures, but I haven't had the greatest experience with them and smaller fish species. And of course, buy bait according to the species of fish that he wants to catch.
Overall, if he seems to enjoy fishing a lot and goes often, then you can buy him a better rod, reel, and maybe some more equipment too. I could go on for a very long time about gear for smaller fish catching, as that is my specialty, but I'd recommend to learn as you go for this one.
Wow, a topic that I'm useful! 😁