Venice ACTV passes

The vaporetto passes are for a 24 hour period, so a 3-day pass is for 72 hours from first use. I'd definitely go with the 7-day pass plus one way airport bus. for you and your wife. Then, nothing to worry about and take as many rides as you want.
From the ACTV website: https://actv.avmspa.it/en/content/venice-urban-services-0

2, 3 AND 7-DAY TICKETS
Travel for 48, 72, and 168 hours respectively from first ticket validation on the urban networks of the Municipality of Venice: the waterborne network (excluding routes 16 and 19, the Casinò route, and all Alilaguna services), the mainland road network including Lido and Pellestrina, the tram network, and the People Mover, excluding travel departing from or arriving at Venice Marco Polo Airport.
With an additional supplement surcharge of € 7.00 for one-way travel or € 13.00 for return travel, all 1, 2, 3, and 7-day tickets (including the 3-day Rolling Venice ticket) can be used on bus lines departing from or arriving at Venice Marco Polo Airport, which are otherwise excluded. The aerobus supplement must be purchased at the same time as the daily and multi-day tickets.
Solution for young people from 6 to 29 years of age, the "3-day (72 hours) ticket" is valid for 72 hours from validation. This ticket is issued only for holders of the Rolling Venice Card, which can be purchased from any Venezia Unica ticket office at a price of € 6.00.

The extra 24-hour pass is quite expensive at 25 euros. Is your hotel located such that you'll definitely need to take a vaporetto from Santa Lucia Station to your hotel, and then from your hotel to the bus station at the end of the trip? If so, the extra 24-hour pass may be worth it. I was in a similar situation last fall with 9 nights in Venice followed by one night in Mestre. I bought the bargain-priced weekly (168-hour) pass and got by with--I think--just one or two single rides over the other days. But my lodgings were in Cannaregio, about a 20-minute walk from Santa Lucia, so I didn't need a vaporetto to get to and from the train and bus stations.

I think the add-on fee for the airport bus is 7 euros. I assume the prices you're quoting are based on ordering the passes early so you qualify for the 5-euro discount.

Thank you both for the responses.

@acraven: We are in an apartment in Cannaregio, in easy walking distance. My seven uses of the vaporetto did not include to/from the hotel. I suppose we could hold off on using the vaporetto until Friday around noon, then we'd be good until the Monday mid-morning bus. If we really wanted/needed a vaporetto we could pay for a single ticket.

And yes, I am looking at the early purchase prices but I have until first of May before I need to buy. I'll give this some additional thought as I'd save 82 euro if I just get the 3 day + VCE transfer.

I think the financial advantage of getting the bus add-on for the vaporetto pass isn't all that much--maybe 2 euros? So maybe you can manage without the pass on your last day; that would help a lot. And if you don't need a vaporetto to get you and your luggage to your lodgings or arrival day, that would also be significant.

It's comforting to have a pass for the full length of the stay in Venice--once you manage to forget what you've paid for it. I confess to being irritated by the pricing of the vaporetto tickets; the longer passes seem like bargains only because the price of the single ticket is so astronomical. I was pretty stubborn about not giving the operating company more money than I absolutely had to. (I do love Venice and will return.)

We are going to Venice for four weeks. Choices are either 4 x 7 day passes, or buy the residents card for 100 euro, and then load the card with trips at 1.30 per trip. The residents card is good for 5 years, and I think that will be the best option.

That's a great catch, Aussie. I wish I had noticed that 5-year deal last year.

We were in Venice last month for about 70 hours and had prepaid (30 days in advance) for the 3 day (72hr) passes. We arrived and departed from the train station. Our apartment was about a 10 minute walk but across the grand canal, so we activated our passes as soon as we arrived and took the vaporetto one stop to save climbing over the big bridge (lots of stairs) with luggage. Same thing on the return, so we definitely got our money's worth. Those 2 trips were great and very helpful with the luggage, but because we had the pass we used the vaporetti many times throughout our stay, with great pleasure, sometimes just to cross the grand canal at a convenient location, sometimes to rest our feet and enjoy the views. We walked more than 20k steps per day, but still had plenty of use for the vaporetti. If you have the pass, you'll use it but besides luggage, it's never critical if you're just staying in the main areas, so if you decide to skip the pass on first or last day, it will work fine too. Have a great trip.