Hi Brandie,
Welcome back to the Disney Parks Moms Panel! Fast Pas+ selection day is a happy day in our household!
I love your planning for this dilemma. I would book Slinky Dog Dash first, then Avatar Flight of Passage second. Both are difficult to acquire. Another strategy that has worked for us is scheduling our visits to Disney's Animal Kingdom and Hollywood Studios for the end of our trip. And, even if I have a preferred time, I take whatever time we can get. On our trip this past August, I was able to book Avatar Flight of Passage for an afternoon time when I booked 60 days in advance. There were no morning times available when I first booked but when I checked back a few weeks later, I was able to switch it to a morning time. Success!
If you cannot get one or the other or either, you can try to rope drop the parks on those days. Just be sure to pay attention to the
Park Hours for the dates of your visit, note any early morning
Extra Magic Hours and plan accordingly. We also did a pre-park opening dining reservation at Tusker House Restaurant on our last visit and were able to just walk onto Kilimanjaro Safaris afterwards - saved us a Fast Pass+.
Brandie, prior to making our Fast Pass+ selections, I create a chart with our preferred Fast Pass+ attractions and times. We typically do our Fast Pass+ selections in the morning so that we can start adding that "rolling," fourth Fast Pass+ while in the parks for evening attractions. Since we generally leave the park in the early afternoon and return before for fireworks, I often make a fourth Fast Pass+ selection for us to do before we find our fireworks viewing spot or I make one for after the fireworks so that we are not battling the crowds to exit the park!
Magic, memories and Minnie Mouse hugs,
Donyell