A friend of mine had a long counter installed across a similar space, with shelving overhead. She had two cute rolling chairs pulled up to it. The space underneath the cabinet was kept clear. She had two girls as well, and they did really well with it. Each girl could have a memo board on her side, and if they needed file-drawer type storage, maybe they could have a cute rolling cabinet that just pulled over when they need it.

Can you do something like this?

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The counter idea would probably give both girls the greatest amount of work space. As for storage, what is being stored? It's probably best to figure out what you are going to store in that area and then chose the storage to fit the items. I like cabinets with drawers or doors to hide lots of little, cluttery looking things; shelves for books and larger objects that don't get that cluttery look. Or shelves with baskets and boxes and bins to help keep things organized.

Each girl could have a desk blotter to define her space, and a cork board on the side wall of the alcove. Or you could run shelves up the sides as well as the back of the alcove.

Do you need to fit a computer or two in there as well? For that and a lamp or two, you will need electric outlets.

bestyears- I wasn't thrilled with the idea of a long counter but your idea with their own personal memo board, etc. makes that sound like one that would work.

caminnc- love that look. Maybe if I tweaked it a bit, changed the positioning of the chairs.....

camlan- We are storing books, school supplies. Thanks for the input.

There have been some really nice rooms designed using bunk beds, with a study area or play area on the lower level instead of another bed. Wish I could find some great room pics, but here's the idea:

Here is a link that might be useful: Bunk Bed & Desk combination

I like the long desk idea, but another option esp. if your daughters prefer their own space would be to do 2 desks of size (18D x 42L) and put them at opposite ends of each short wall. Place it so that the seats are also on opposite sides to one another so they don't bump one another. That would leave about 33" for the aisle--a bit snug, but should be OK and still allow them some lower drawer space for art/school supplies. Then you could put hutches above for more storage.

Here is a children's desk I just purchased for my 8-year-old DD. Dimensions are 18D x 41L.

covenantbuilders, I drew this up sometime ago for a friend. She had a smaller area than you have and wanted it as a place to do and store her crafts, but also use as a desk. This idea should easily work the larger size you have giving each of your daughters over thirty inches each depending on how you built the sides.
The desk top in this opens up like an old elementary school desk did. It allows for a little better storage than a drawer would. Easier for most DIYers to do themselves too.

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Here's a more decorative example of how bunk beds are being used to free up floor space. There are other pics in the series. Didn't look through all of them, but #6 has a desk setup also.

Here is a link that might be useful: Bunk bed w/desk beneath

Here's another option, linked.

Saw one with a slide for coming down, too, lol. Too much fun : )

Here is a link that might be useful: One bunk with Desks on each end

justgotabme- I like your design. So, are there shelves on the bottom?

Yes there is. My friend wanted as much space for storage as possible. The alcove was deep enough so she wouldn't be kicking things. I'm sure you have enough space to do this too.
I played around with the design some more making it double and adding more color on the walls, ceiling and floor to help it all make more sense.
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Oh and I deleted the other one in my photobucket album to save on space. I've more to delete before I run out of space again.

covenantbuilders,just checking to see if you got my answer.