If you want the dining plan here is a way to book it and break up the amount due at 45 days...
1. Book a *package* that includes your room and 1 day tickets - This amount will be due 45 days before you arrive.
2. A week before you arrive you can call and add the Dining Dlan - Amount for that will be due in full when you call. (you CANNOT add the Dining plan when you check in- you need to add it at least 3 days before you check in)
3. You can then pay to upgrade your tickets when you check in.
All of the above will depend if you are booking with a special rate that has certain requirements...like the Free Dining requires 2 day tickets with those packages.
HTH.