your bedroom has so much cute potential - fun bedding, the lamps, curtains, nice furniture. i'm excited to see your "after" pics.
of course, it's ideal to move the office stuff out. is there any other part of the apartment your son has less access to, like the eating area (dining room/kitchen)? obviously he would be there sometimes but maybe it's less of a play area like the living room. if there is a way to have the office stuff elsewhere, that would be good.
if not, what about moving one or both of your dressers to the living room or your son's room? and/or the bookshelf (unless that really needs to be by the office stuff)? just so it feels less crowded.
how often do you use your printer? if it's once a week or less, you could put it away, even move it to the bookshelf, and just set it up when needed. that way you could move/declutter the piece of furniture it's sitting on (file drawers?) or tuck it under the desk if needed for storage. or put it right next to the bed as a night-stand with a table cloth over it, so that side of the bed gets a lamp too (bad feng shui you've got going on right now!).
what about your vacuum cleaner? it looks like you have wood floors in your bedroom. if it doesn't have a home, it could be tucked into a corner of the room where you use it mots often. i suppose it feels more "put away" in your bedroom, when you're out in the rest of the apartment, but then it makes your bedroom feel like a closet.
good luck! you are going to kick butt on your bedroom and sleep soooooo well in it once it's tidy!