The Christenings I have photographed I have had much more freedom than when shooting weddings (even in the same church and with the same officiant).
As long as you don't interrupt the service, respect the church and the congregation, and are discreet you'll find that there tends to be less regulation around when you can actually shoot, and about moving around. As a matter of course I always checked with the person running the show on the day.
As for settings and kit - it depends entirely on the venue, and the weather that day. I have shot a christening on a 24-70, and one service because of the layout/position on a 70-200. Take what you might need, use what you do need - or do a reccee, work it out and bring at least a backup for your main lens.
Kelly - this is another of a series of very basic questions. You are getting the same answer every time. YOU need to be able to assess the situation and the environment and make some decisions. Unless you tell us the exact venue, and date, and someone has shot there before the only answer you'll get is the one Phil and I have given you. I appreciate you are new to this but you need to start working some of this stuff out for yourself, and get some confidence. If you never get past people telling you what to do you will never have the professional air you need to convince a PAYING client that you are the person they are going to trust for their wedding/portrait/christening etc.
I genuinely recommend that you consider working as an assistant, or engaging (paying) an experienced photographer as a mentor or trainer to help you through some of this, and to give you some structured development and feedback. You can't learn the business of being a professional photographer in a forum at the completeness and rate at which you seem to be demanding it.