You talk about minimal queuing but if you add the time it takes you to walk from wherever your family happens to be in the park to pick up your Fastpass, return to wherever your family has gotten to, and then go back to Splash in your Fastpass window, you aren't actually saving any "queue time," you're just converting it to "walking back and forth" time.
Well, that's why some planning is good. FLEXIBLE planning. And logical thinking.
There are several things in the immediate area of Splash Mountain. So first thing you do when you get to that area, you go grab a FP. In all but the busiest times of year, they are an hour or so out.
In an hour, you can go grab lunch at Pecos Bills, you go ride the Haunted Mansion (a short walk round the water front), go see the Hall of Presidents (same), go through the biggest concentration of shops outside of Main Street in Frontierland/Liberty Square - and actually, Pirates is pretty much around the corner the other direction, too.
Now, if you are at Buzz Lightyear, walk all the way to Splash Mountain to get a FP, then go back to Space Mountain - yeah, that is "walking back and forth time". And silly.
But it really doesn't take a genius (or even any real pre-planning) to grab a free park map from your back pocket, look at it, realize where the "big attractions" are, and plan to enjoy other things in the vicinity. Even ignoring the "lands", there are essentially only 3 zones in the MK where everything is within a short walk of anything. Fantasyland/Tomorrowland, Frontierland/Liberty Square/Adventureland, Main Street/Hub. And most of them overlap. Particularly the Frontierland/Liberty Square/Adventureland, where there are so many passages from one side to another through short paths or open buildings.
The Studio's are pretty much the same (there is really only two hot spots there). AK, too - though definitely more walking there but also far fewer attractions you need FP on (and most are on one side of the park, at least). Epcot - yeah, if you are in American Adventure and go get a FP to test track and then go back to WS - that's just idiotic.
FP+ doesn't help this, just makes it worse - because at least an hour, or even a few hours in advance, you can look at a map and decide what to do in the meantime. With a FP+, you have to plan out the entire day months in advance and cannot change on the fly to accommodate for the dozens of things that may come up. You become that "Disney Nazi" everyone hates - "We must proceed to Splash Mountain now because our FP window is in 37 minutes..." with zero flexibility and having to determine what park, and what exact location you are going to be in the park, in a short window WEEKS or MONTHS in advance.
If someone cannot manage to pre-plan getting FastPasses already same day in an order which makes sense and isn't walking across the park back and forth endlessly, this new system is definitely not going to help them AT ALL. Just make it even worse for them, because they either will waste them and not actually use them or they will be handicapping their entire vacation around a few select attractions they could see anyway with minimal thought on the day of.
Besides, it's not like we have Harry Potter or Transformers or any new rides that people really see as showstoppers anyway. The biggest wait at WDW is for TSM, which one can reasonably replicate in their homes with a few wheeled office chairs and the Wii version of the game. The only reason it has those waits is because there is so little for the audience that ride attracts in the park it resides in. Very little else is that popular unless you are there on spring break or a holiday - and if someone isn't competent enough to know that if your goal is to see the most attractions doesn't know you go any time BUT those times in the year, something tells me FP+ isn't gonna save them, either.