Private tours in Florence - are these reasonable prices?

It seems reasonable to me. However, you might also want to price private tour with Context Florence to see if they'd be more reasonable with david added. I've used both ArtViva and Context, and I can tell you I far preferred Context. (I did the regular adult Context itineraries, not one of their family-focused ones.) In my experience, the quality of the information was far better with Context. Both agencies used interesting guides with relevant training who were fluent or native English speakers. However, I found ArtViva to be more gossipy/tabloid-like(eg, hearing about Lippi's sex life while we were viewing one of his best Madonnas at the Uffizi... no information about the painting, period, technique, etc). I've used Context many times in multiple cities and never had that type of experience.

Walks of Italy and Through Eternity both have Florence options and are in Rick's books

It sounds high. The guide I had last year (complimentary group tour) said the cost was about €150 for a 3-hour walking tour. I thought she was very good. If you send me a PM, I'll be happy to send you her contact info. She told us lots of quirky stuff as we went along and was very congenial and open to questions.

Regarding the second guided tour (private car; 360 Euro for 10 hours total) is, based on my experience, an excellent price. We did something similar in 2011 and the guide basically dropped us off in each town and we agreed when and where we would meet to go onto the next one. For a hill town that would fit nicely into your itinerary, I suggest San Gimignano or Volterra.

Marie We just went to the Uffizzi and down loaded RS uffizzi tour onto our phones and walked around with that tour at our own leisurely pace. If you are doing the tour with a "private guide" you are on their time line, not yours. You need at least 2-3 hours for the uffizzi and 1 hr for the David/prisoners. I bought the tickets from the official website for 11 euro each with a 4 euro fee for reservation. We picked up the tickets in less than 10 minutes and waited 10 minutes in a special line to walk in. I would use the time/euros for better use than a private tour. You could also get a bus that goes daily to Siena and spend the day there (you need a day there) and see the beautiful hilltowns along the way. That is my opinion.

The guide booked through your hotel seems quite reasonable. We took a day in the Tuscan countryside, visiting a small vineyard, a few hilltowns and castle with Slowdays in Florence. It was 129 Euros per person, including lunch and wine tastings, with a reduction for the children. http://www.slow-days.com

Marie, I'm in agreement with the other "Marie". We downloaded the Rick Steve's application on my iPhone, from there it's quite simple, you pick your country, (italy), city, and then site - then just download in minutes. Do this from home ( or at a free wifi connection spot abroad) to avoid charges. We used a dual headset adaptor and plugged two sets of headphones into the one phone. Attached at the hip, literally, but successful. This could be bothersome with multiple people, and may be easier if downloaded onto separate phones. Or if they're young, an actual guide may be best for the interactive aspect. I recommend some type of guide (live or audio). There's so much to see, and without a little background info, you truly would miss a lot.
Have a great trip!!!

The Accademia skip seems high. The car to Siena, Pisa, and hill town seems reasonable. You could rent a car of course and do it yourself. I agree with you. Group tours are pain sometimes and private is better. But, you can do it yourself.

Accademia and Uffizi are 15 euros per person including reservation, you'll need a reservation now because its so busy. Have a look also at florencepisatours!

A well educated, personable guide can be worth their weight in gold. Especially when you've got kids with you. I think the 250euro price seems good. You should ask why the price jump is so nigh for the Accademia. Never hurts to ask...