I was in a slightly different situation--because my boys had TTTS, and we discovered it at 14 weeks, frankly all I could handle was concentrating on keeping them alive until they were 24-26 weeks. Every day after that was a blessing!
As it was, they were happy as clams in there and probably would have stayed 40+ weeks. (My daughter was a 42, almost 43 weeker--and yep, my dates were accurate!) The only reason why my boys were born at 36 weeks was because of serious health complications on MY part that won't happen to you.
Go for it, mama! There are MANY MANY mamas of twins that make it to 37-42 weeks (though just to warn you, OB/GYNs tend to be cagey after 37 weeks!) with absolutely NO problems. Don't let anyone tell you it can't be done!
Even with all their problems, my boys were 6 and almost 5 lbs, so they were big healthy babies, never had to have supplemental oxygen, home within a week, and breastfed right from the start, exclusively.
You are going to do wonderfully. Think of happy, round, cozy babies snuggled up inside you and growing and growing.