Reasonable plan, I'd think so.
Its really tough to gage the availability of FP+s for anything beyond the 3 ... we have had a pretty darn good run of it most days, but then other days everything is gone in parks where you don't think it should be ... like by 1pm on a 5 day in the most recommended park. Toy Story was completely gone by 9:38am the other day, but then last week we were able to get TS FP+ at like 2pm for like an hour later (though that might have been crap luck, there were others available later in the evening as well)
Other than the TS day (when it was gone at 9:38) we haven't really had any issues moving things around from bed when the alarm goes for us to get up for RD. Just pop open the app, hit plans, click on the FP selection, Modify and then select new time.... Of course, this is still pretty slow, and I am rockin the fastest smart phone on the planet in the Galaxy S5 overclocked.
Personally for our time of year, these crowd levels, I think we have had the most success booking FPs for 9:30 or 10 - 10:30/11 ... 11-12, 12-1 ...
We most things SB ... and plan to be at the first FP as it expires ... so like 10:40 or 11:10 ... and yes, we really used the 15 minute overtime frequently and on purpose. Ride those 2 FP back to back, and then head to the Third (or head toward it and ride something else SB on the way) burn the third and head for a FP+ Kiosk. Lines at this time at the kiosks have been pretty good, especially since I go to the kiosks that I know are least used. In under 2 mins you can have an FP for an attraction often starting 5 mins out from you booking it ... head that way, if there is something with a low SB on the way, do it, if not, head to the attraction you want and SB that up. Or Double your pleasure if its like a 20min SB, wait once and then SB it right after ... then on to the next kiosk. If you get something right away, awesome, if not, take lunch, then hit that FP, and then hit the kiosk, if you can get something right away, great, if not, book something for the evening, head out, come back for the night shows and know you have an FP in your pocket.
As for the last question, you wont even need to take all the bands to the Kiosk to book your FPs, as long as they are all linked, they only need one band and can book FPs for everyone. We have on a few occasions shared bands for people to use other's FPs. That being said, those people scanned into the park and were present, they just didn't want to do that ride ... don't know if this will work with people not actually in the park ... but its worth a shot.
Hope that helps !!!