You should advise your friends to try 'non-penile inversion technique' first.
Dr. Suporn, Dr. Kunaporn, Dr. Peera, Dr. Chett and maybe Dr. Kamol in Thailand seem to use this technique.
Your friends might need about 6 months to a year to determine their maximum depth and width after regular dilation. If that doesn't work for them, then they can always go back for the colon graft as a secondary procedure. Colovaginoplasty is risky business, it has long term issues. It's not worth taking the risk and having it done straight away. I am speaking from personal experience. Having said that I have 3 other friends who went for the single stage colovaginoplasty and they seem satisfied and have active sex lives.