Am I nuts?? (my story--long)

How do you know?? I'm 40 (41 in May) and have been married for 21 years. My marriage is stable and my husband is great. As a kid, I always thought I'd have a big family. When we married, my husband was open to the idea of kids but not in any hurry (he had a child from a previous marriage who lived out of state). We tried to conceive in my mid 20's for a number of years without success. Although we considered adoption; we were concerned with the cost. Additionally, my husband began to have second thoughts, and I didn't want to push for something my husband wasn't fully on board with. Alas, time passed. Hormones subsided. I went to college instead, obtained an MBA and secured a decent (if not well paying) job. I figured I had weathered the pain of being childless well overall. I began to accept my childless state and adjusted well to the solitude (if not lonely at times) life it brings.Then it happened!! Wham! My 40th birthday was fast approaching and I found myself thinking of babies again. Feeling more confident with age, I approached the topic of kids with my husband again. (No small feat considering he was 56 at the time!) Being the sweet guy he is, my hubby agreed to attend foster/adopt classes with me so we could consider our options. After completing the classes we even volunteered to provide respite care (babysitting for foster parents who need a break). That was an eye opener to say the least. I learned things I never knew about my hubby and about my endurance. We definitely had different parenting styles which caused some heated debates. Nevertheless, we both wanted to remain on the list for consideration if a younger sibling group became available for adoption.That was a year ago. Fast forward... early this week we finally get a call from the state. Three healthy kids just became available! Beautiful babies--a 3 year old, an 18 mth old, and a 5 mth old! I'm terrified and estactic! After waiting a year without hearing anything, I had given up again on the thought of having kids. I was even considering going back to school for a career change. Meanwhile, after hearing the news, my poor dear husband is running the other way as fast as he can. The thought of 3 kids isn't scaring him so much as the thought of 3 babies! I know we are good parents and have a lot of love to give kids. I know the biggest regret in my life so far has been not experiencing the joys (and frustrations) of raising children. I know my husband is just scared. I know he will make a great dad. I see it everytime he's around kids. I also know I will be alright if for some reason it doesn't work out (disappointed and heartbroken--but alright). I understand the hugh adjustment this will be on us. Even if I can't explain it; I know we'll be okay and glad we took this step. I just feel it in my gut. (This coming from a person who insists on a logical explanation for everything!) So.... am I nuts??? What is this thing that makes me willing to turn my life upside down in an instant? Can I/we really do this? And why does it seem that young people aren't plagued with these agonizing questions?