Beginner question: use of article

Getting back into Greek, I forgot how uncertain of myself I get in translations…
Following sentence from Peckett and Munday’s Thrasymachus:

δηλῶ γὰρ τῷ παιδὶ τὰ ἐν ταῖς τῶν ὀλβίων νήσοις.

I got stuck on that τὰ in there, but if it makes the following clause substantive, I translate mechanically as:

So I am showing to the boy the things in the island of the blessed.

…and a bit more idiomatically as…

So I’m showing the boy what there is in the island of the blessed.

Am I on the right track? Thanks! bjs

Looks like it.

Yes, except: islands.