My oldest just did a journal in K and 1st.
In 4th and 5th grade her teachers gave her some regular assignments and some special projects.
The first year her teacher gave her the work several days in advance and she did it all before we left. For English, she wanted her to keep a journal while we were there. And for Math, she wanted her to write 5 word problems. This was fun because she made the problems about her trip-- shopping, time on the busses, etc.
Last year she had a bit more "regular" school work to do and she didn't get it until the day before we left. She did most of it in the car (23 hours each way
) DD did not know we were going to Disney (we told the kids we were going to grandma's), but her teacher did. The class was studying plants so the teacher gave her a special journal and told her to draw and write some information about native plants in FL. Teacher actually knew we were going to Epcot during the Flower and Garden Festival, so DD took pictures of plants and wrote down info about them and when we got home she made the journal before returning to school.
I don't really want the kids to bring a bunch of books and have to worry about school work while we're at Disney. The last two years we have left on Monday or Tuesday, so she had the weekend to start the work. And we return home on a Thursday night, so she has the weekend to finish work before returning to school. For work that needed to be done while we were at Disney, DD would just take a few minutes in the evening while I was bathing the little ones to do some journaling. We also return to the resort for a nap every day, so she would sometimes journal while everyone else was resting.