Sorry another Rome FCO to Florece ?

You can do that, but be sure to specify that when buying tickets at the airport ticket window, since it is slightly less expensive than using the Leonardo Express to Termini.

If it works out with your arrival time, there is a direct train from FCO to Florence at 11:08, and another at 15:08.

As Sam says, the best bet would be the direct rain from FCO to Florence, but there are only a few a day.

If you will need to change trains at Termini or Tiburtina, you can buy the tickets for both segments at the airport.

The train from the airport to either Termini or Tiburtina is only regional; the train from Rome to Florence is high speed. So, no need to specify.

I'm not sure which airport route is "quieter." Since the train to Tiburtina is local and cheaper, it may be more crowded with people using it for stops other than the airport. The train to Termini runs nonstop from the airport to Termini.

If it works out with your arrival time, there is a direct train from
FCO to Florence at 11:08, and another at 15:08.

With mobility challenges, this would be your easiest solution if you can make either of these times work: straight to Florence on a high-speed train with reserved seats and no changes. I just wouldn't purchase tickets in advance should you run into any snags with a delayed flight.

Note that most stations have elevators so look for them and you won’t have to use the stairs.

With mobility problems I'd rather go to Termini, a terminal station where there are only level transfers.
Otherwise, just ask for a ticket to Firenze SM Novella via Tiburtina on the FL1 train.

Trenitalia's counters and ticket machines are near the tracks, inside the airport station. Going there you'll pass by a travel agency that sells train tickets, but they add a small fee.

Hello again
Many thanks for the replies/advice people have given us. Ironic going to Florence but battling Storm Florence here in the Carolinas.
May I ask a couple more 'dumb' ? Will we be able to locate the Florence train say at
Termini? Or do we have to ask someone ie. Is the train for Venice stopping at Florence etc?
Also we are coming back to Rome for 8 days after Florence & wish to purchase 2 of the 'CIS weekly tickets' as I think we'll make good use of them (staying near Pyramide metro) would we be able to get these at FCO or better waiting until we get back to Rome Termini? I read they only come into use after 1st Validation
Any further advice will be great
Regards
Kay

The platforms/tracks in the train stations are well marked. But you can also look at the "big board" listing departing trains in order of next departure time. Look for your train - FYI, your train's final destination may not be Florence - it may say "Venice" because that's the final destination. Look for the time instead first. Trains rarely if ever leave at exactly the same time, so if you are looking for a 13:04 to Florence, find the next train departing at 13:04 on the board, then go to the platform number indicated. It may also show a train number specific to your train - and if you have a reserved train, that should match the one you booked.

FYI, don't let any kind person "help you" load your bags on the train. They will be expecting a tip and will be upset if you don't give them one.