Getting started with middle school electives
The beautiful thing about homeschooling is to spend more time learning things that are fun and interesting. So even if you don't have all the regular subjects in place, or you have limited spoons for your unschool learning day, do make a priority of doing at least one cool experience, online class or project that the child wants to do. It will keep them motivated at this age. If motivation is an issue, do ALL your learning like this for a while.
Technology: Lego robotics team, Coding, game design, Photoshop, Video editing (try Outschool, Code.org, Tynker)
Music: Musical instrument lessons, YouTube tutorials, take a choir class at the local middle school
Physical projects: Build something, Maker kits, Backyard projects
Art: Graphic design, Drawing/Painting, Outschool has some fun art classes online
For a more thorough list of resources, see the Curriculum Planning pages.