1) What is the best option to get to Praiano from Rome? 2) How should our time in Tuscany be spent? ex) Florence/Siena/small towns/wine tours/ private tours ?. 3)Tips for traveling in Praiano? 4) Any big pitfalls to avoid? 5.) We will be driving north toward Florence and south towards Siena. What would be the best place to park and access the city?
So several questions there - let's see.
Starting at the end, number 5. Avoid ZTL's. Very expensive. If you need more information on them, ask. We can save you hundreds.
Park outside Siena in one of the official carparks. My favourite is just under the edge of the city. Avoid the ZTL. Florence, you need a car like a boat anchor. The most ZTLs of all. Easy to avoid, park outside the centre.
Number 4 - other than ZTLs be sure you understand the road signs and information signs. Understand how to navigate using the next town not the compass point. Have cash for the tolls. Understand about TUTOR, the speed cameras. Don't drive in bus lanes. Be sure that every driver has an IDP - if you need more information on any of these, ask.
Number 2 - you've really answered your own question. You need to think what each person in the group would prefer to experience and then tailor the places you go to meet those needs. No sense in going into Florence if nobody has any interest in Renaissance art, sculpture or architecture. A wine tasting tour would be wasted on a person who has no interest in wine. See what I mean?
Number 3 - sorry, I haven't been there.
Number 1 - you don't say in your profile, or in your post, where you are coming from. But if it is a long way off, perhaps involving a long flight, I'd suggest a while in Rome or Orvieto or elsewhere to recover a little from jetlag before driving after a long flight.
No number - congratulations on your upcoming nuptials.