Since you are so flexible, there is no need to book any hotels. Start looking for a place before it is getting dark and about half to one hour before you plan to stop. Friday and Saturday evenings are more difficult than the other days. If you plan to do camping in some famous parks/beaches on weekends, they may be fully booked (you can get the information on-line). Always collect some hotel phone numbers for each place before you leave home, just in case.