Harry Potter and the Time Travelling Portkey

(These are not my characters just scenarios that I have created whilst wishing that there were more Harry Potter books etc average copyright thing. Also sorry for the bad name).
Dumbledore's up to his old tricks again. As a fan of James and Lily he decides to let the marauders see aspects of their future including sending Harry and several other witches and wizards back in time. Basically a fanfic comprising of Marauders era stories + some Harry Potter and next generation stories.