Households do not really run on rules. They run on a weekly rhythm that everyone has memorized, and the school year is what holds that rhythm in place. Take it away and the chore rotation, the meal plan, and the pickup schedule all stop being obvious at the same time.
Expect the reset, do not fight it
The mistake is trying to keep the term-time system running through July. It will not, and failing at it for eight weeks makes it harder to restart in September. Better to explicitly switch: a summer rotation, a shorter chore set, a meal plan built around whoever is home.
Two things worth keeping
Keep the shared calendar, because summer has more moving parts than term time, not fewer — camps, trips, visiting family, and four different adults' vacation days. And keep whatever surfaces what is due, because the house does not stop needing maintenance just because the routine did.