Rome - Florence - Siena - Venice or Rome - Siena - Florence - Venice

My question is whether it matters if we go to Florence or Siena first between 6/25 and 6/30 (for logistics considerations such as train schedule and connections).

Does not matter but I would not go on Friday Saturday or Sunday. Just like everywhere more people on the weekend

We plan to travel by train (I have read it's best to take buses between Florence and Siena).

Take the train there ride the bus back or the other way around so you can see the difference.

I'd like to spend 1 full day (2 nights) in Siena or just do a day trip from Florence. Any advice?

If you've never been to Florence then do it as a long daytrip. That way you don't have change hotels.

The bus to Siena only takes an hour from the Florence train station. The buses line up to the right of McDonald's across the street and around the block.
The good thing is the bus will drop you in the center city. The train drops you out on the edge of Siena and a city bus must be taken into the center city.

I would probably go from Rome to Florence, then bus to Siena, then bus or train (taxi to train station) back to Florence to connect with a fast train to Venice. To check train schedules, use the trenitalia or italotrena website. You need the Italian names - Roma (tutti ..../all stations), Firenze SMN (Santa Maria Novella) and Venezia SL (Santa Lucia). Trenitalia has trains from Siena to Florence, or just take the bus.

Thank you, Jazz+Travels, David, and Chani for your responses. They are really helpful. Two follow up questions:

1. Do I need to bother to find out the bus schedule between Siena and Florence or could I just go to the bus station and wait for the next one (if it's frequent)?
2. I have been playing around on the trenitlia site and trying to get familiar with it. Do you know how far in advance they release/post the schedules/fares? I didn't get much info at all for June 25, my planned travel date. Also, does my 14-yr-old count as a child or an adult?

Thank you again!

Mei

Do I need to bother to find out the bus schedule between Siena and
Florence or could I just go to the bus station and wait for the next
one (if it's frequent)?

It's frequent enough, but not every 5 minutes. On average there is one to two buses per hour. Try not to travel on weekends (especially Sunday), when buses are less frequent:
This is the timetable from Florence to Siena Mon-Sat (Sa=Saturday only, NoSa=no Saturday service, only Mon-Fri, otherwise it means everyday Mon-Sat)
http://www.tiemmespa.it/var/ezdemo_site/storage/original/application/816225e061f8fdaa26f0ae6972debe9e.pdf

I have been playing around on the trenitlia site and trying to get
familiar with it. Do you know how far in advance they release/post the
schedules/fares? I didn't get much info at all for June 25, my planned
travel date. Also, does my 14-yr-old count as a child or an adult?

The summer schedule probably hasn't been loaded yet. But you can check the schedules for now, they won't change much.
If you intend to purchase a high speed (Frecciarossa, FrecciaArgento, FrecciaBianca) train ticket ahead of time at a discounted price, tickets go on sale 120 days prior to departure. Be aware that once you buy a discounted ticket (super economy or economy), you are locked on the specific train you book. No changes or refunds are allowed on discounted tickets. So buy those only if you can commit to a specific time of departure.

Due to construction and location of the 2 new trams lines, buses that used to depart from near the McDonald's may now depart from other locations around the train station. Your safest bet may be to walk to the nearby bus station and catch the bus to Siena from there. To reach the bus station, exit the train station to your right (with back to tracks), cross the street, go around the corner to your left and arrive at the bus station entrance in the middle of the block. The walking time should be no more than 5 minutes, probably less.

Thank you, Roberto da Firenze and Frank. I went to Siena from Florence for a half day trip 20 years ago. I still remember running to the train station from town center in the dark, trying to catch a late night train back. I hope this time around, it will be a more relaxing journey. :)

Thanks again,
Mei