I'm not certain, but I thought you have to do nursing before specialising as a midwife? In which case, I'd just start on your nursing however and whenever you can, Ashlea.
IRT becoming a doula, I'm not certain about the age thing, but I do know that most of the mums in my MG are 10 or so years older than me and we wouldn't have known unless we'd asked each other how old we all were. I think you'd have lots to offer I think it is more a case of how you interact with people as to whether or not they'll feel comfortable, not how old or young you are. JMO, and I wish you all the very best!