On some cruises offering their form of anytime dining, you can usually call up and make a reservation. Or, if you prefer, you can have a standing reservation. This can be very helpful if you have kids or a special requirement.
We normally do late seating, but on the last two cruises where we did anytime dining (Celebrity & Holland America), the Matre'd came to our table and told us if we liked the table, waiter, and time, he would be happy to reserve it for us every night.
So, when you get onboard, go talk to the Matre'd and see what they can do for you. Doesn't hurt to ask.