Hi watercolorwiz -
You really don't need reservations for the Boboli and Palazzo Pitti: that's why, aside from the Uffizi, the PassePartout doesn't include timed-entry booking for the those particular attractions. They're not as busy as the Uffizi, and last I knew there was a priority-entrance line for people with PassePartout or other types of tourist passes. From the website:
"The combined ticket is valid for 5 consecutive days and offers one single admission (with priority) to all the museum sites of the Uffizi, Pitti Palace, Boboli Gardens, in addition to the Museum of the Opificio delle Pietre Dure. With the combined ticket, it is mandatory to choose the day and the hour you wish to enter the Uffizi, which is the first museum to visit. Only after your visit at Uffizi, you can access to Pitti Palace and Boboli Gardens without any restriction or time limit and without any other form of reservation, as long as it is included in the 5-days validity of your ticket."
What I don't recommend, not that you intend to, is trying to do the Uffizi, Pitti and Boboli in a single day! The Pitti complex can eat a LOT of time as the 28 rooms of the Palatine Galleries + Royal Apartment are extensive - although the 14 rooms of the apartments are still closed for renovation and I've not seen a re-opening date - and there's the Costume Gallery, Modern Art Gallery, Museum of Russian Icons and Treasury to see. The Boboli grounds are also VERY extensive and VERY short of the florals many expect when visiting "gardens", just so you know. :O)