Anna, sure can. First, there are two bus systems from Venice airport to the Piazzale Roma. One bus system is ACTV. This is the same company that runs the vaporettos (water buses). The second bus line is run by ATVO. 3Euro for a one-way ticket to the Piazalle Roma. It's a 20-minute ride. Both lines have room for your luggage. www.actv.it for more info.
I haven't read yet that they have found the location of your B&B. When that appears, I can help you further with the vaporettos. You'll love these guys. It's part of the Venice charm. In the meantime, you can log onto www.actv.it and select English. Under "Departure", select "P.LE ROMA". For the arrival stop, we need more info. But, you can do this as well but I'll be glad to assist.
When you get to the Piazzale Roma, you will need a ticket or pass of some type. The one-time ride is 6.5Euro - a bit expensive. If you are going to be there for a day or two, I suggest the Tourist Travel Card which you can buy at the Hellovenezia booth nearby. Here's the scoop on these guys.
16,00 € - 12-HOUR TRAVELCARD
18,00 € - 24-HOUR TRAVELCARD
23,00 € - 36-HOUR TRAVELCARD
28,00 € - 48-HOUR TRAVELCARD
33,00 € - 72-HOUR TRAVELCARD
50,00 € - 7 DAYS TRAVELCARD
Now the trip to Florence. As soon as you set up in Venice, go to the train station and buy your tickets to Florence. There are two ways to look at this. First, you can ride the Eurostars. 32.30Euro for a 2nd class seat. It takes just under 3.0hrs with no train changes on some runs. Second, you can ride the local Regionale (R) train for 8.90Euro. You will change trains in Bologna and it will take about 90 minutes longer. Your choice. Choose what you would like to do and I can send you train schedules. You can easily purchase the tickets at the ticket machines in Venice. For the Eurostars, you might ask the machine for the AMICA fare. This is a limited discount. Sometimes you can get them.