Some more things to think about.
Are you thinking of hotel/motel nights? If so, what rates would you expect? $50/night x 6 nights = $300.
Bikes safe at night while sleeping?
500 miles per day? Are you thinking about any sight seeing activities? Stops at major landmarks to do photography and shots of our bikes to prove we were there?
3 meals per day? or 5 smaller meals spread throughout the day? How long of days are you thinking about?
How big is your trailer that your wife would be towing behind us? Can she keep up?
Personally, if we are in Southern states that are warm then we could start earlier or later in the year.
Northern states would need to be mid summer - Bostons 100+ inches of snow will take time to melt and if I never see snow again that will be fine with me.
Some other ideas - take a day and ride to an Amusement park - Spend the next day at the Amusement park and then the next day ride someplace else.
Ride to a river and do White water rafting?
Las Vegas has a deal where you can rent real race cars and drive them on a track.
So what say you now?