Aesthetically speaking, it doesn't matter where you start. So, I'd start off with a few questions...
Are there any items that you are keeping?
Sort through these and see if any of them would go with a particular wall color. You'll save yourself some money rather than painting and then realizing that some furniture or accents you wanted to keep don't go with your new color.
Are there any items that you or your daughters really love?
Sometimes a whole decor can start with something as simple as a pillow or a "knick-knack."
I.e. - Maybe your daughter is ready to move on to a "big girl" theme, but still loves a teddy bear with a blue bow around its neck. You could start with this idea and plan a shelving arrangement with the bear featured. (You know, up high enough that she won't feel "baby-ish" but where she can still look and enjoy it.) Then, play your colors off of the tan in the bear or the blue in its ribbon. I've seen whole rooms planned off of the colors in a favorite pillow sham.
Also, consider flooring. It's probably the one thing in the room that would cost you the most to change. If it's a neutral floor color, like wood or a tan carpet, you could pick up almost any wall color with a throw rug, but if it's a particular rug color or tile, you want to consider that.
If you are still undecided, go to the hardware store. Ask them if they have any discounted batch colors. (Sometimes people pick a specialty color, have several gallons made, then get it home and decide its not what they wanted. If the store has a guarantee, they have no choice but to take it back and are stuck with someone's custom colors. Often, they'll be happy to get rid of it at a deep discount.) Maybe something someone else didn't like will look perfect to you and you'll save big!
If you are more of a visual person, and need to see everything together. Check out the Behr paint website. It has a section where you can select different colors for wall, moulding, accent, etc. and it will put them all together in a picture for you to get an idea of what a finished product will look like.
Good luck!