When I found out I was pregnant with our third child I had a little girl heading for 4 and a bub of 10 months. My husband and I discussed our birth options and once we decided on having a homebirth we started to look for information to give to our eldest daughter.

A wonderful place to start is on Youtube. There are so many videos on there that if you put in the appropriate keywords for yourself you will find something that works. I spent many evenings viewing footage and then bookmarking those that were most appropriate for her.

Some of her favourites were:

sorry... will have to come back with links - taking too long to load at the moment

We also had a number of "new sibling" type books from my second pregnancy and read them over and over again. None were specific to homebirth but all were loved:

I'm a big sister now
There's a house inside my mummy
Daddy's having a horse

She also attended every appointment with me apart from my 20 week scan as the hospital wouldn't let children in the room for that.

Every question she asked we attempted to answer and if we couldn't give her an answer on the spot we did our research and came back to it later.

By the last month of my pregnancy she was drawing pictures of ladies having babies and was adamant that she would watch the whole birth and that we were to wake her. Unfortunately this didn't happen but she was there from only moments after her sister arrived.

Another book that was highly recommended was My brother Jimmy Jazz but we were unable to obtain a copy in time.

For a starter we went with computerised and moved on. She must have watched this one 100 times

This probably isn't going to help much, but I'd just say keep talking to him, and have him present for the birth.

But have a backup plan, because you mightn't want him there, and he mightn't handle it too well... Just in case.

Even when they don't talk much, they understand everything. So just keep chatting, remember it's normal, and just take it as it comes :)

Just to *bump* the topic :)
My Brother Jimi Jazz was the only book I could get my hands on and it was one of the only books my son wanted read to him in the months leading to the birth. He knew we were having a birth pool and was home for the appointments.
At present, he has been asking for two more siblings and has been wishfully telling me I have a baby in my belly and that I need to have it in a birth pool at the farm we're moving to soon!
So, yes, talking, talking, talking. He knew a bit about placentas by the time he saw his sister's because of the placenta in Jimi Jazz and the 'marvellous cord' he talked about so much afterwards.
My partner wanted a back up plan and I told him that he could make one and I wouldn't use it :P I was adamant that DS had to be there, and in the end had a very trusted girlfriend come round to support us, which was magic.