First of all stay at least 3 full days.Take a kangaroo/sling and if you can'r go without a super light stroller (all this bridges)
Get an apartment/bnb/hotel in less touristy area like castello, arsenal, cannaregio or dorsoduro
✔️ water taxi/vaporetto - just a transport for you but for children it will be a whole adventure!
✔️ gondola ride - fun for whole family
✔️a mask crafting experience
✔️treasure hunt (fun way to explore the city)
✔️take a rowing lesson (for sportive families)
✔️ glass making factory on Murano island
✔️ doge palace (nice for the whole family)
if you have even more days you can also visit
✔️ beaches on Lido
✔️Gardaland (entertainment park) next to Garda lake
And of course don't forger to book your photographer in Venice to capturing your Venice trip!