I honestly don't think age matters.
The game probably appeals to younger players more than older players, anyhow. When I first bought my key, I was pretty young.
And now that I think of it, all the exceptionally-grammar skilled users use to be very young back in alpha BlockLand. Badspot never put an age on Blockland, and there should be no reason to. The game can be completely harmless.
Saying that you want all older players on Blockland, is like saying you want all the white people at a watermelon stand.