Just to present another side to the Plan B school "holding on to the deposit" issue - I have a DD still waiting for a decision here but I am also a college admissions professional. Here's what happens when you hold on to a deposit into late summer and don't tell the school you are not coming: some student out there had their heart set on Plan B school (just as much as ours do on USNA) and they were waitlisted. Sometime in late June, Plan B school looks at all its deposited students and says "that's it, we're full." They then deny the kid who stuck it out on their waitlist and who maybe desperately wanted to go to Plan B school. That kid accepts admission at another school, attends orientation, etc. Dream gone. THEN, your kid comes along in late summer and says (hey, I survived PS) so "nevermind" on my deposit to Plan B school. Schools know when the waitlist notifications go out and most are in late June, perhaps early July. We expect it and that this is when we get any cancellations we are going to for that cycle. We don't expect them August 15th.
So, as a person who has to make some of those heartbreaking denials, I just wanted to present another viewpoint. I am not picking a side or judging - just making everyone aware. I do tend to agree with those that say you should head into PS with a mindset ready to conquer, without an "escape hatch." If your D/S doesn't end up making it, they can re-apply to Plan B school for January admission in nearly every case.
Come on - be in it to win it! Your kids are fantastic (love hearing about them!) - they can do it!