Hi, I'm no mod or anything but on behalf of PokéCommunity I'm glad you came to us for advice!
If your son loves the new show, I recommend getting Pokémon Black or White, and the sequel to the game of choice (Black 2 or White 2). This is what I did.
Differences between Black and White are a few exclusive Pokémon in each version. Refer to Bulbapedia or Serebii.net for information on that.
There are also changes in locations. Black has Black City, which is where you can get a few very good items to evolve Pokémon. White has the White Forest, a place where you can catch a few other Pokémon from previous generations which aren't anywhere in Black.
Another difference is the appearance of Opelucid City. In Black, it's futuristic, while in White it has a more natural look.
If your son needs help to play the games, I suggest playing with him, it's one of the coolest things a parent can do to their child. I loved when dad played videogames with me, he introduced me to Atari gaming way back in the day and bought my Genesis and SNES, and played with me and my sister. Who knows, you may even start enjoying Pokémon yourself! The games are for all ages, I'm 25 and play Pokémon since 1999, because I love the concept.