It's super nice of you to offer your composition skills for this jam!
The last music artist I worked with for a game jam, it was only a three day live event, and that was a super time crunch for production. The things that made him memorable as a joy to work with were: asking about theme and tone before composing, quick creation of a working sample loop (like 3 hours turnaround) and ability to take feedback and critique and use them to turn the sample into a polished final piece.
I'm sure you will do excellently, especially with a longer time frame to collaborate across. Once I have my design pinned down, I can share my art-board and mini GDD with you if you like, and we can see if if it's a project that interests you :)