If you aren't sure whether you want to visit museum after museum, then it might be better to just book tickets for the Uffizi Gallery and then buy tickets on the spot for the other museums you do decide to visit. You might end up paying less for what you do visit.
For example, online booking of Uffizi is around 20 euro, plus the Duomo pass which costs 15 euro and includes all 5 sites in and around the cathedral is 35 euro compared to the 72 euro of the Firenze Card. Even if you add another museum or two in there, you might still be below that amount. While Firenze is crowded in that period, most lines at most other museums (other than Uffizi and Accademia) are quite tolerable and move fast.