This client wants to purchase a professional photographers work. The key question to ask yourself here is if you can deliver professional work. If the answer is yes, then you should get paid to do so. Some of the factors to consider are not in your question, so Is this a "shoot and burn" wedding. Are you simply providing what falls out of your camera? Or are you providing color balanced and possibly retouched digital files? Will there be an overnight stay if the couple ask you to work longer? Is that included in your contract? Is overtime? Do they pay a 50% retainer to hold the day?
If the later is the case then you need to plan for those hours of post process work in your pricing. So many new Wedding photographers these days are willing to work for less than minimum wage, and that is hurting this industry.
So first be sure of your abilities, then charge a fair price. If your skills are not there yet, you have some months to work on them. How are your lighting skills, your posing skills? It's amazing to me that some skilled photographers that are clearly selling good work are charging little or will sell it for a pat on the head and an attaboy.
Figure out your time, then make sure your at least getting 25.00 an hour. Your clients will be spending allot of money on this special day. So make sure you can deliver your art, and remember that years down the road if their house catches fire and their standing outside wondering if they can go back in for valuables, their wedding pictures will be on the top of the list, nothing else they buy this day will be so valuable to them. So yes you have a great responsibility, but do not believe for a minute that it's not a valuable commodity to sell a customer. When you give them the price. Give it with confidence, and then shut up and wait. You don't need to explain it. Don't be desperate, or you will be taken advantage of.