Your plan is for 7 days worth of credits, but the normal assumption is that you will only use all three credits on days 2-7 while the remaining three credits are split between day 1 and day 8.
The truth is, your credits are available from the moment you check in all the way to midnight on the day you check out (day 8 for you).
And of course, you can use those credits in any order you wish.
There are many times that I’ve booked the first day as room only and then booked the rest of the stay with dining and then used all the credits by the time we would leave, usually very late afternoon or early evening on check out day.
And when you combine our being on the deluxe dining plan with our driving and having a cooler in the car, we cashed out all remaining snacks on our way home, and sometimes there were a large number of snacks and bottles of water heading home with the doggie boxes of dinner left overs.
I’ve also instead booked the last day as room only and we still had all our credits until midnight on that room only night to use the dining credits, again, because they do not expire until midnight on checkout day. This way, you’ll only have to deal with breakfast the morning you fly out.