I would be utterly miserable following a tour guide through the streets of Venice.
You can save a lot of money and have more fun doing this on your own.
Book the Doges Palace Secret Itinerary tour for the morning of Day 1 in Venice. €20 per person and there is no line; you have a reserved spot on the guided tour.
http://palazzoducale.visitmuve.it/en/pianifica-la-tua-visita/special-itineraries/secret-itineraries-tour/
You can book a "skip the line" ticket (timed entry) for San Marco Basilica for €2 each.
https://www.venetoinside.com/attraction-tickets-in-veneto/tickets/skip-the-line-saint-marks-basilica/
For the Grand Canal tour and Murano, I suggest the following:
Buy a 24-hour vaporetto Pass and start it in the afternoon of Day 1. It will be valid until the same hour the following day. Use it first to visit Murano, timing your return to catch the sunset, for an enchanting view of Venice.
The next morning, catch the No. 2 vaporetto at San Zaccaria Dock B, heading to Giudecca. It will stop first at San Giorgio---well worth getting off to visit this church and enjoy the views across the bacino to San Marco. Catch another No. 2 and ride it westward through the Giudecca canal, watching for an opportunity to move to the forward outside seats if you can. You will go around past the cruise ship terminal, and into the Grand Canal at Piazzale Roma for your "cruise" down the canal.
You should still have several hours left on the vaporetto Pass for another trip.