You are one remarkable Mama and a wonderful Sister.....and it sounds like you have a tremendous fiance as well! 
A friend told me about your post---and I just had to pop online to extend my admiration...and any twin "tips" I could!
One thing I would absolutely recommend is trying to get in touch with your local branch of a mothers of twins club.
Most of them have HUGE yard sales in the fall and in the spring; and you could undoubtedly get some great deals. (By the way, you do NOT need "two of everything"!) There is typically a nominal membership fee, but even if you elect not to join the group, when you explain your situation, they may allow you to attend the sale. To find your local chapter you can visit www.nomotc.org . If you do join the local group, many of the clubs also have "Mentor Mama" or "Big Sisters" programs where you can get some one-on-one support from an experienced twin mama in your area, and that could be very helpful. :)
Your boys are of an age where they may be great little helpers as well.
If you haven't already purchased Twinspiration: Real-Life Advice from Pregnancy through the First Year I'd be honored to send you a copy.
(It's my last one from the freebies my publisher gave me...I can think of no worthier recipient!) Just email me a mailing address and I'll get it in the mail early next week.
Congrats on your pending marriage, and on your pending twin-blessed family!
All the best-