Well, I thought that extra days on the longer-day tickets really only come to a few dollars per ticket per day more. So for an extra few bucks per person, you could have access to the parks on all the days. Then you won't feel like you have to cram so much in on you "park" days. Do you actually own your tickets yet? If not, you might want to rethink the tickets you're getting. 10 a.m arrival has the whole day ahead of you!!! If you bought them through Disney, I'll bet they can easily be upgraded. If you bought them through a discount supplier (which would less money), then I'm not sure if it would be possible to upgrade through the supplier. I think you still could upgrade through Disney, but you'd have to pay up to the full price.
A few extra dollars will give you a lot more flexibility, and may take away the worry that you're wasting a day. IMHO. Just something to think about....