Like @saturn5 , I would suggest allowing for 90 minutes between parks unless you take a Minnie Van to speed things up (or are driving yourself).
Also, you can't have FP pre-booked into different parks on the same day. You can pre-book up to three experiences in a single park on any given day. For all parks except MK, you can book only one Tier-1 attraction and can not book additional Tier-1 attractions until all three reservations have been used.
FastPass (FP) can be pre-booked for a different park on the day the guest is going to use the FP. https://www.disboards.com/threads/f...ing-anytime-fps-cl-fps.3538258/#post-56320829 The OP can use FP's in the MK then look for a FP for another park while still in the MK.