I would suggest

ArnoI'd, V.I. (Vladimir lgorevich)
Geometrical methods in the theory of ordinary
differential equations.
Springer (1988)

of course, it's not to be taken "as is" for an undergraduate ODE class, but a lot of modern important examples (taken from nature) are given and discussed. Overall, there are a lot of well illustrating and expressive drawings which can inspire the lectures.