Don't stop watering. Just don't increase watering when the rosette shrinks and the plant slows down, and maybe find a spot with overhead cover to keep it out of the rain.
Dormancy is more a gray area than a black and white thing with Aeoniums. So it is distinctly different from Adenium or Plumeria dormancy. The plants here look different and slow down during summer (fewer, smaller leaves spaced more closely along the stem) but they seem to consume roughly the same amount of water. Your mileage may vary once heat starts to be an issue.
Different species of Aeoniums have different degrees of dormancy (simsii is one that looks radically different in summer, as do its hybrids). But the same plant will behave differently in 2 locations if one is hotter and more exposed to overhead sun in summer. If you give them some overhead shade cloth (or pick your dappled shade equivalent) and make sure they stay cool, they will tend to keep growing during summer. You can oversummer them indoors if you like (to avoid heat/rain), that is also an option, but it's best to max out the light indoors.
