Well, if you can afford that setup, I would plan on the girls each having their own clothes, and simply borrowing if the other sister is ok with it. Having five daughters, I know all about sharing rooms, closets, clothes, bathrooms, etc. For example, my first two were fifteen months apart and were best friends through high school (in the same grade.) However, the younger one was a slob and older onewasn't, and they had different tastes in clothes. The younger was careless with the other's clothes. Her sister would have hated to have to share everything with her. My point is that I would give them each their own closet, since they will likely want to have their own clothes, anyway. Then, they can learn to ask to borrow an item. I also wonder why you are including a tub and shower in a children's bath? Even though the bathroom is a nice size, I believe it will feel cramped. I think I would give each child her own vanity and toilet, and include a shower/tub combination in a separate middle room. And, when your kids are teens, you might regret giving them their own doors to the outside! :)

Believe it or not, decent looking ceiling fans exist. On every design show I've ever seen they're the first things to be thrown out, but I have them in every bedroom. Mmm slight draft at night without the sound of floor fan... I pspent no fewer than 18 weeks looking (off and on) for a "pretty" one to go in my master. I have lived with a 4 poster bed. My experience - unless you have really high ceilings, and I'm talking like 10 ft, and a sizeable room, it will turn your space into... tiny. Once upon a time in a previous life I thought I had a big bedroom until I put a poster bed in there. I like your computer nook. I always wanted a space like that, which I could separate from the rest of the room with some romantic drapery tied back. I might force that idea on my formal dining room. :) beds/headboards coverin ga window do bother me. I don't like anything to cover a window (couch, table, or otherwise) -- but that's just me. And if it came down to a queen bed, or covering that window, sure - the window would get covered! We have single panels on our two bedroom windows, mostly because they're skinny and it looked silly to me to have two panels. If you need to cover the window, something that seems to help (at least when I've seen it done) is to pull the bed away from the wall a foot or so. Then you can go with two panels, and it looks kind of intentional instead of "didn't have space." Something else to keep in mind with blocking windows -- does the sun come directly in such that it would fade your bedding over time?

I'd say if you don't feel comfortable with it, don't attempt it. But I'd do it (and am about to do something similar in my house...) Are you comfortable with moving the electrical? I would go about it like this: First, determine whether the wall on the bedroom side is load-bearing. If it isn't no problem. Look in a basic home-improvement book they have in the bog-box stores for basic steps-by-step instructions on how to frame a wall and install a pre-hung door. With basic skills and decent power tolls, both those things are pretty easy. If the wall is load-bearing, you're going to have to figure out how to properly support the loads, with a built-up header, etc. Don't forget there will be some finicky finish work patching in the hole where the old door was, adding in baseboard, etc.

A sliding door vs. a sliding window? Both should give about the same functionality for egress and an alternative entry point during the renovation. The rub on the sliding doors is that they will be more expensive (especially at a custom sized opening) and will usually have more heft on the frame and door sash (i.e. less glass) than a sliding window.