I’ve sailed both and will sail both again. The issue here is Oasis has significantly more for kids to do. If your kids took part in the wet and dry slides, laser tag, ice skating, zip line, flow riders, large pools and the carousel they may very well be disappointed by a ship that has a few wet slides , ropes course, mini golf and small pools.
I personally didn’t do some of the things offered on Oasis so Carnival not having them doesn’t bother me but I’m not a kid so it’s different.
As for Venezia I was on her for 12 days and I didn’t notice a smoke smell anywhere other than the casino and I didn’t find the free food offerings any more Italian than they are on any other Carnival ship unless you count the 2 new burgers at Guys. I actually saw a lot of complaints that they marketed this ship as “Carnival fun Italian style” and then put very little effort into making it different from their other ships. It’s literally just decorated differently. Some voyages have an Italian festival one night but the cruise director has skipped that a few times too so your basically just getting a Carnival ship from 2019, neither old nor completely brand new.
I don’t think any Carnival ship has enough additional activities to compete with Oasis class for kids if they actually did all that stuff.