7 days Siena - Venice

First, if you do not have a car, it will be more difficult to daytrip from Siena than from Florence. From Florence, you can take the train to Lucca or Bologna. If I stayed outside of Florence, I would have a car and stay in an agritursmo so you could drive through the Chianti region or the Crete Senses region and explore lots of hill villages.

1. Stay in Florence if you don't want a car.
2. Rent a car and stay in an agriturismo and visit the Tuscan region.

In my opinion, Carla's suggestion of an agriturismo is a perfect solution for your disparate group. Many of them have pools; some offer special features like horseback riding or cooking classes. Your teens could opt for staying while others of you go off to sight-see some of the time. The only warning I would throw in is that you'd better get cracking if you decide on an agriturismo. Many of them will have been fully booked for July, 6 months ahead or more.

Why are the teens unenthusiastic? How old are they?What are their interests? It seems to me that having unenthusiastic teens is a possible set-up for a really bad trip. What do the kids want out of this experience? More info would be helpful. Many others on this forum have traveled with teens and could help with getting the teens on board.
You might want to re-think the Venice departure since flights with connections to the US leave early, complicating how you get to the airport.

Working backwards, we are booked to fly out of Venice on an 11am flight (heads to Atlanta), so if the airport is about a 1/2 hr away, I think we should be okay. In terms of what I meant about the day trip, I was thinking that we could day trip to Florence from Siena, letting us hit a couple highlights (such as David) and head back to the slightly quieter Siena.

Teens - my 13 yr old son will be fine. It's the 16 yr. old daughter who is not thrilled to be stuck with us away from friends. She also can get overwhemed with too much stimulus, but the invite came from family and we felt like it was something we didn't want to pass up. I think it all just feels a bit scary to both of them. Language, foods, unknown things by the truckload. My mom and I are the two adventurers really driving this.

I like the thought of the agrotourism, but the thought of dealing with a car rental is intimidating. I'd be the one driving and it feels like a bigger load on my shoulders vs. hopping on a train and simply relaxing. That being said, it may be something I should think through further. If we could find one, especially with the horse component, that could be a game changer....

Siena isn't connected all that well by train, but there are buses. I day-tripped from Florence to Siena. The ride is about an hour (so's the train ride, but the station is farther from the center). I believe there are buses to other Tuscan towns - after all, the locals have to get around too.

You can get to the Venice airport from the island in about 1/2 hour by water taxi for about €150, about twice what you'll pay by vaporetto that takes closer to 2 hours.

I love Siena but it is not a good base for day tripping with public transport. I'd stay in Florence and day trip to Siena by bus. I'd also put the teens in charge of planning a portion of the trip. Give them each at least a half day to plan.

My thought is to drop a day from Siena and add it to Venice. There is plenty to keep the group occupied for three full days, and it is a city like no other. Siena is good, and we enjoyed it, but Venice is beyond awesome. Texting is cheap both to and from Europe so the 16 year old wont be totally cut off from her friends back home.

Have your teens use FaceTime or Skype to keep in contact with their friends. Just remind them of the time difference.
Example from central time zone. Italy...6 pm=home...12 pm.
Italy...11 pm=home...5 pm.

Also keep phones on airplane mode so you don't get incoming calls from friends in the middle of the night 😴

You can see Siena in one full day, so I would recommend spending two of those four nights for Siena in Florence.

Wh n in August? The Palio takes place in Siena on Aug. 16 and that day as well as the week leading up to it will be crazy crowded, and lodging high-priced.

Maybe try Lucca instead?

Or if the dates are OK for Siena, and you are willing to rent a car for short distances, this agriturismo just 5 km outside Siena is pretty easy to sell to teens:

http://www.mulinodiquercegrossa.it

They have a family apartment for 4 and grandma could get a separate single room. The pools are lovely for relaxing and cooling off n a hot afternoon. You could still use the train to get to Florence for a daytrip.

16-year-old might enjoy shopping the little stands around the central market in Florence -- lots of cheap (€1) keychains to take home to friends, €5 scarves, pricier leather purses, wallets and belts.

Venice hotels -- we have stayed near the train station in the past (Hotel Florida) for ease of luggage handling, then used a vaporetto pass to see the sights. Will be trying Pension Guerrato near Rialto Bridge, which mamy people recommend.

Based on our son's experience taking his 2 older daughters (ages 10 and 12 at the time) to Paris, the kid who participated the most in the planning had the most fun. That was the younger one. So the advice to involve the kids in the planning is right on.

As to the language issues, knowing a bit of Italian would be helpful for all of you. I've been working with Duolingo online. It's free. At my age, the going is slow, but I bet those kids would suck it up in no time. Even the very basics could be very helpful.

Since this is the first European trip for everyone, having everyone read the excellent information on this website would probably make things go much more smoothly. Many of the parts of the Travel Tips section are especially useful. And y'all could watch some of the videos from the Italy group on Watch the TV Show. Scroll down the link to see the list.

If you haven't already, you might want to use Rome2rio to get an idea of how to get around between the places you want to go. It may take longer than you expect. Out of curiosity, I checked on the trip between Siena and Florence and it takes about an hour and 15 minutes by bus. The train takes longer.

Keep in mind that changing locations also takes lots of time beyond the travel time. Checking out of one place, getting to the train station, then reversing that process at the next destination can add up to hours. With a large group, you will travel at the speed of the slowest person in the group.

Because of the relocation time, the standard advice is that a "full" day is bracketed by 2 nights. For example, to have 2 full days in Venice, you need to spend 3 nights.

Edited to add: for lodgings anywhere, my favorite resource is Booking.com. You can search for your exact dates, list how many of you there are, and refine the results in all kind of ways, including having air conditioning. I'm sure you already realize that finding one room for all if you is highly unlikely.

Apartments are probably out because of your short time anywhere. But BC also includes B&Bs and hotels. I like it best because the reviews have been verfied as being written by people who have really stayed in the places they review.

As for Venice, the train station you need to arrive at is Venezia Santa Lucia. The only vehicles in Venice are the boats of many kinds. You will have to hoof it everywhere or take a vaporetto. Those lovely arched bridges aren't ramps, they are made of stairs. I mention all this because I'm also a grandma and at 71 with bad knees I have to plan for these things. Having said that, somehow I seem to walk circles around some of my whiney grandkids.

Please be aware that the Venice Biennale will be going on in August. That may raise the already pricey rates in Venice.