The only thing you can do to prevent it is increase hygiene (I’m sure yours is already good, not implying that you are Stig of the Dump 😉)
Things like:
Drumming it into the kids that you must wash your hands before your eat and whenever you get home from being out and about
School clothes off when you get in from school and quick shower (especially in norovirus season)
Wiling down touch points - banisters, light switches and pulls, remotes, kids tablets etc. antibacterial wipes don’t work on norovirus so I buy Clinell wipes from Amazon which do kill noro.
Steam clean laminate floors regularly
if kids bite their nails work on trying to break that habit
Even if you do all of that perfectly, it won’t stop them getting it sometimes, especially if they’re still very young, but it should decrease the frequency, especially as they get a bit older.
You could also try probiotics, which help the immune system in general and can make bugs pass more quickly, but they don’t prevent norovirus or rotavirus.