score:2
Definitely will be a great trip, specially in family and great date as well to go!
The museums has an earlier leave times but remains open. The same probably would apply on some other places, depending on what are you interested to see. Check directly on the sites You are interested.
For example, on Doge's Palace Museum on Nov 1st the last admission is at 4:30pm. On normal days is 6:00pm
You can get great resources using the Google Local Guides site
From there you can jump to other sites. Like this tour on Venice
The important thing is to make a previous plan on your route accordingly to what You want to visit/watch/eat/see/experience. And research a little bit on official sites about costs and times.
Probably You can connect with some local guides using the Google site above.
Bon voyage!