We've stayed at the S/D several times since dd was 2, she's now almost 4 and up until our last visit she was in the portacrib.
We put her crib in the corner of the room near the slider. We brought a king sheet and clothesline and clothespins from home. Some of the rooms had curtains on 2 sides so we'd feed the clothes line thru the bracket under the valance on each side at the end and tie it. Then we'd hang the sheet over the line blocking her from the rest of the room.
In some cases if the room only had curtains on one side we'd hang the other end of the clothes line near the door on the pole stuck out from the wall (to hang a garment bag).
This worked great. We brought her activity box and stuffed animals and she'd play for a bit even with us right there because she couldn't see us and we'd try to just keep one light on, then she'd eventually fall asleep. We also brought her CD player and put that on next to her crib.
Last visit we used a twin air mattress and just pined the sheet (with clothespins) to the curtains mid way up and rubber banded the other side to the amoire tv door, she had a little tented area and she loved it.
When she was a baby she'd never like to sleep anywhere but her crib til we took her to Disney
Just her and I are going to WL next month, they're setup is a little different. If we do bunk beds i can hang sheets around the bottom bunk from the top but if we do queens I'll have to figure out another strategy and probably use her air mattress again. I can let you know how the rooms are set up after our visit
Sorry so long, but this was such an issue for us too