A reader will be unavoidably absent until the second week of school. The question to me: What would I do with an AP Physics 1 class, knowing that the sub is a random adult rather than a physics teacher?
Of all the times you'd have to miss. Guh, not the first week(s) of school. This is when physics students most need your guidance.
I don't have an easy answer for this one. I'd really rather just start school two weeks late than have a random sub for a week. It's too easy for bad habits to get ingrained, for them to get a false sense of what physics is.
But I'll bet your school isn't about to cancel physics class for two weeks. My only suggestion would be to do unrelated enrichment work for a week or two, and then start the course as normal when you return. See, I think many of us take time out during the school year, or perhaps after the AP exam, to do some one-off activities: a bridge building contest, research about the history of science, etc.
It's not ideal... but you could move some one-off activities to the start of the year. It's important to choose activities that are not directly related to physics content, I think, so you don't ingrain misconceptions. So those projects about motion picture physics, or making a video about a physics concept - I don't recommend at year's beginning. I offer two options that I've done in the past that might be useful here. I suspect this post's comment section might provide even better ideas.
Option 1: Here is a link to a "pseudoscience" activity I've often done at year's end... they take it as a quiz, then they choose one or two things they marked true to investigate. In science, all claims are false unless clear evidence is presented to convince an audience they are true. This activity can be done with minimal supervision; the students will discuss well with each other. Give a few suggested sites to jump-start student research, such as snopes, the straight dope, and the skeptical inquirer.
Option 2: Pose some astronomy questions, and have students investigate them using some online tools. I like the Regents earth science astronomy questions, paired with a University of Nebraska set of simulations. Just pick some of the questions from recent tests about observational astronomy, the motion of the sun and moon, or the phases of the moon; then ask students to teach themselves the underlying geometry using the simulations. If you email me, I can forward you a few assignments I've given using this method.
Other than that, I don't know. I seriously don't recommend lab work or math review. I don't recommend any physics content at all until you're there. I'd love to hear good ideas in the comments. Best of luck.