They sure are the youngest character's we have since Dawn and Lucas (not counting Ethan, Lyra, Brendan, and May). If they aren't young for their age then it's likely a return to the roots going on here for the 20th anniversary of Red and Green (and the 10th of Diamond and Pearl which aforementioned player characters).
I feel it might go that route, but then again we had Tate and Lisa who seem intelligent and yet are younger than twelve (Hoenn MC's age). You could also count Lucas/Dawn the assistant too. Hmm, a young assistant, we sure haven't seen one this young since Sinnoh. I feel a lot of sinnoh vibes going around. Funny enough Kalos as a region reminded me of Sinnoh, and Alola reminds me of Hoenn.