It’s going to be hard to beat W&M in terms of getting the best bang for your buck. Certainly most of the public universities suggested so far – few of which offer much, if any, financial aid to out of state students – are highly unlikely to be better options.
Have you run EFC calculators, and are Wash U and U Miami affordable for your family? If so, Wash U would be my pick of your list. There are few places better for undergraduate ecology, particularly among private colleges.
To add to the list of liberal arts colleges mentioned so far, Connecticut College and Ohio Wesleyan are well worth a look.