I have been through this exact situation. My Mom was under hospice and there was no chance for recovery (cancerous brain tumor) and she was slipping away from us slowly.
My sisters and I went to the Funeral Home (they were not receptive at first but said later that it was the best way to take care of things) and pre-arranged just about everything.
Trust me, it is not easy but it is so much easier to make good choices when you are still able to think clearly. The thing is this.. a lot of tough choices are made after someone passes, without a lot of room for change due to time frame. With the pre-arrangements we selected there were few things we had to deal with when she did pass, we knew what the next step was and we were able to console each other.
AND.. when we wanted to change something or add something to the service we were able to (we forgot a favorite song of hers) and we had a great bonding experience creating memory boards with old pictures.
You are in my prayers.
L.