SI5351 is pretty extreme, and generally it’s programmed with a profile generated by the manufacturer’s website. I saw libraries to set desired frequencies instead, but I’m not sure this is a good candidate for a demo. Maybe a command to configure and use it as a multiple clock generator?
For the AT24Cxxx - maybe this is a good time to survey EEPROM configurations and make a read/write/verify command? It’s won’t cover EVERY eeprom because there’s so so so many ways of address pages, write page size and alignment, etc. But I’m going to look at what is involved.