Cam spends his summer trying and failing to figure out how to deal with Dementors when he cannot see them and they are kind of hard for even wizards to wrangle, and doing a lot of venture capital and reading.
Here is his plan! He would like a TA who can cast that convenient vanishing spell so he can go ham on the visual aids. Also he needs to know the field trip policy. And whether he can bring students off campus to show them computers. Also he's orchestrated it so it should make sense for kids coming in mid-course, without any given year leaning too heavily on any previous year, since he doesn't know what Charity was doing exactly.
Third years: Muggle cultural tidbits, to humanize and amuse! Music, cuisine, movies, fashion, books, little bit of world religions, and in particular Muggle imaginings about magic (and science fiction).
Fourth years: basically a ridiculously accelerated world history course, starting from the Neolithic and hurtling along from there, focus on how this all leads to the countries and languages they have presumably heard of for magical purposes. Highlights include British colonial behavior (lightly sanitized but not by that much, he's seen what wizards put in their kids' books), the farming-related tech tree, and the general ideas of feudalism, democracy, communism, et cetera. Breadth over depth, the goal is for this list of keywords to stick to the point of "I have heard of that and can spell it to look it up" with an aspirational "I think that thing might be related to this other thing", he's aware these kids will be 14.
Fifth years: Drilling into the history of science and technology in particular, the scientific method and its engineering brainchildren: paper had to be invented! Math had to be invented! Wheels! Timekeeping! Somebody had to dig up cadavers to learn anything about anatomy! Many things you can discover by observing a human toddler took ages to figure out! Genetics! Telescopes, microscopes, and yet more scopes! The chemical elements! Electricity! Dinosaurs! Rocketships! Computers!
Sixth years: the theme is INFRASTRUCTURE! Scaling problems and scaling solutions for modern water, power, transit, sewage, shipping, mail, governance, public health, and communications, without a speck of magic! International trade and the global economy! Practical skills elements may include placing phone calls, posting letters to their MP, camping out in a Muggle hotel for a weekend, maybe visiting an airport or even taking a short hop on a plane, if and only if he expects them to be able to get through sans Memory Charm.
Seventh years: Muggles, what will they think up next? No, seriously, he's from the future and he knows. There's daeva in his future but everything they do has to work on good old physics after it shows up and Muggle humans designed a lot of it. Maybe they can visit the Moon? Learn a bit of programming? Also he'll leave room for whatever is on the presumably charmingly stupid NEWT exam.