Should I be a surrogate mother?

Our "couples" best friends have had 2 failed attempts at IVF. I am just so disappointed for my friend this last time she has just about given up on having children at all. I have said to her many times: "if I could give you some of my fertility, I would!" They are thinking about adoption, but she is Filipino and he is caucasian...they would like to have children who look like them. I have three healthy children (who are now teenagers) and had three easy, uneventful pregnancies. My husband was the one with the idea to be a surrogate for them...we have not discussed this with them yet because I am still pondering. I am 38 years old...I'm wondering if that's too old. It's been 15 years since I had a baby, but everything seems to be in working order and I'm very healthy. I would like to know opinions...good and bad....on surrogacy. Even better, if anyone has experience, let me know.