You have two choices - spread, or be selective.
I'm playing "La cathedral engloutie" which this has some whopping chords. I can do a 9th depending on what's in the middle, but this has 10ths and some octaves with a lot in-between.
A bit of research revealed that in a recording of Debussy himself playing the piece he spread the RH chords in one section (where the left hand is doing a broken chord accompaniment). This sounded "right" for that section of the piece but really didn't work in others. In that case you need to look at the chord and see what the essential bits are harmonically - many of Debussy's chords aren't spread further than an octave but contain some really difficult spreads between your 3rd and 4th fingers - there is generally a note that can be sacrificed...
NB - the recordings aren't sound recording as such, but made from the rolls of a recording piano.
Cecilia, you have the soul of an optimist

My hands haven't really grown since I was 12/13, but my spread certainly has as the hands get used to it!