Need guidance

I am 39 years old and am single. I volunteered to be a surrogate for my sister (she is suffering from fibroids and has tried IVF several times. Last time it was successful but she miscarried in the 5th month). She had 4 frozen embroyos so we decided that I would carry her child for her. I went through a frozen embryo transfer. My uterus is fine but I miscarried after 6 weeks of pregnancy. The doctor does not know why. It seems that 2 embryo's were developing. I cannot explain the shock and agony we experienced due to this tragedy. I just was wondering if I can use my brother-in-law's sperm donation and see if I can get pregnant. I was wondering if I should go for IUI or IVF. My sister told me that my brother-in-law's sperm count is good so we are hoping that IUI may work. My blood type is O+. I am so confused because of so many factors - my age (will be 40 when I go for IUI), my earlier miscarriage, egg count etc. I did some research on successes of IUI but could not make a decision of which way to go and the chances of success. I have not done a test of my ovulation etc. However, I have had no problems with my periods in all these years. My ovaries seem to be fine. My parents have no grand children. They will be so happy to have a child in the family. Please show me a way.
I am basically requesting two types of information from anyone who can help:
1. How can I find out if I and my brother in law can have a successful IUI? What tests are required? I am in Houston and my sister and brother in law are in VA
2. What would be the best route for us? IUI or IVF?
Thanks so much,
Please help me..
AS