Above all, do the voices. This is very important. You must do the voices. Nothing says I get paid seven dollars an hour to babysit you and it is not enough to pay for my XBox Live subscription like a monotonous, droning voice doing Hagrid in the same tone as Hermione Granger. But what if they don't like my voices? Make up new ones. Take your voice box to places it has never gone before. But what if, you know, they've read the book on their own and they've developed an idea of what the characters sound like, or maybe their mom reads it to them--well, experiment. Do Hagrid in a nice, booming Cockney and if they don't like it then do Welsh or Scottish. But I'll sound silly. Nothing is sillier than being worried about what a seven-year-old thinks of you. Well then what if I get embarrassed and start laughing during one of the extremely important death scenes? Then you're in a right bind, aren't you, now? Try doing a Welsh accent. The sheer effort will suck the fun out of anything.