Wow. That's a long run! I'm sure you'll be just fine on the day of the marathon.
Have you tried energy gels like Gu? That one works really well for me on long runs and I like the flavour. (Orange is my favorite, Tri Berry is also good.)
Also, if you like jelly beans, you should try sports beans. I love the green ones!
http://www.energy4sport.com/acatalog/Sports_Jelly_...