The viewing area for the parades and fireworks (assuming MK) are both good, but some folks aren't fond of the parade viewing area.
MK Parade FP+ Viewing Area is located inside the hub area, opposite of the castle. It has an excellent view of the parade,
but not necessarily an ideal location for photographs if you want the castle in the background. If you want the castle in the background, you're probably too close to the castle for good photos. If you don't care about the castle, then the viewing area is great. The only other drawback is that there is no cover/shade so you have no protection from the elements. Remember that FoF comes from Frontierland to Main Street and MSEP goes from Main Street to Frontierland.
MK Fireworks FP+ Viewing Area is located inside the grassy area between the castle walkway and the Rose Garden. You're to the right of the castle (when facing it), so the fireworks appear to the right of the castle. It's an off-center view, but I liked it and I appreciated the fact that everyone sat down so most everyone had a good view.
I agree that getting a FP+ for the parade or fireworks is unlikely as your 4th FP+. If there are two parades in one night, then you might get a FP+ for the second parade (I saw it as an option one time during my trip), but I wouldn't count on it. If you want to get a FP+ for the parade and/or Wishes, I would do that and just accept that you won't be able to get a 4th FP+ until late in the day. Actually, I would try to get a MSEP FP+ and Wishes FP+ on the same night (if you're going to tie up your FP+s until late in the day, why not do them all together?) - that is what I did!