Was there last month.
The Doges is the best €20 you will spend by far in Venice.
To save money eat lunch outside of the water based Venice then have evening meal there. Don't go to restaurants because they are cheap (a €9 meal might sound a bargain but its awful). Buy nice meals for €13+ a pop to get good meals. Rialto is nice but is always packed.
If you are catching a bus on the way in, buy from your hotel (€3 for a return), but don't scan them on the bus. That will save you money. Only scan if asked. I saw about 3 people do it in the 4 days I was there.
St Marks, its ok. Inside stick to going upstairs on the roof. Make sure you and wife are covered up too. Rather than brave the queues, with St Marks at your back head over to the left far corner to ticket/info shop. You can specify a time and get a queue jump for €3 and its well worth it.
For souvenirs the further out of Venice you go, the cheaper. Gondolas were €80 for a short ride iirc. Sure it was 30mins???
Be mindful of the City tax. Think its about €2 per person per night.
Oh have a chuckle at the Antifa signs and the sign that says: Bombing for peace is like ****** for virginity.