You can also use the ledge for a book shelf or put a tv on it with movies on the ledge, try n be creative with other things for your little one.

I like this idea:

Two rooms in one here ...... Extend the ledge on the left by putting base cabs along that edge - some for toys, others for other storage purposes ?? think function in phases - play room, family room, then teenage hangout, etc. - it happens so fast. With that deeper base, the upper wall could incorporate shelving, bookcases, a flat screen TV, etc. (built-out built-ins) so you can watch the news and your son from your exercise machine, desk, or whatever you intend for yourself here, as he plays. Just layout with separate 'zones' as 'play' and 'parents' for his safety.

Along the other side the wall could be framed out - (brought to the same plane as below) above the ledge to create 'niches' in certain places with lighting in them. Very easy to wire while it is all open.

The lower half could be left simple for furnishings later. Consider using a muntin or grid on the inside of the glass doors (at least the lower half - safety) if that is to be his end....