Re: Moving sailboat to Savannah from Seattle...
2913 miles. Long trip. I annually drive San Antonio to Rutland - 2100 miles Takes me 3 days, 2 nights, at the end of which I am whipped. Reading your notes it is clear you really want to drive the trip, and are just looking for justification/support. If you do, please get a long wheel base vehicle.
I strongly urge you to sit down and WRITE down on PAPER a decision tree of the options. Putting the choices down ON PAPER often makes thinking clearer. Include what you would do when problems arise in the trip, all courses.
It is often said on this and other forums that the worst thing one can do while sailing is to be committed to a calendar. I submit the same thing is true in this situation, that is to be committed to a rigid time frame. That way leads to cutting corners, pushing too hard, etc. Just a really bad idea.
Listen to the omens. If a trailer appears that is perfect for the trip, next door, for less than you anticipated, somebody is talking to you. By the same token, if no trailer is available, or has to be custom fabricated for twice what you expected, or won't be available until three days later than you need, listen up.
Making the trip with your son is admirable - if he can drive. If so be sure to get an extended/crew cab, so one can snooze stretched out in the back seat.