Melanie: Sophia Bush
Wanderer: Elisabeth Harnois, Blake Lively, Reese Witherspoon, Emily Browning, Jessica Alba, Jessica Simpson, Alona Tal, Kristen Bell. Personally Elisabeth, Kristen and Emily are best suited. Especially Elisabeth.
Ian: Chace Crawford, Skandar Keynes (he might be too young), Eric Dill, Ian Somerhalder (though we're not that enthusiastic) or UNKNOWN TALENT
the rest of the cast we have no suggestions.