May I join in, please?
Ashley, I know what you mean about breastfeeding! I was quite young when I had my first and didn't feel too comfortable with the idea, I breastfed him for a couple of months but switched to bottle. He was happy, but in hindsight I kind of wish I had stuck it out a little longer! With second, I breastfed him for a little longer, but after about three months switched to a bit of both, and then fully to bottle because I wasn't well in my head. Sleep deprivation made me go slightly crazy, and having read up a fair bit about it I realise now that it can cause all the thing I was experiencing at the time (hallucinations, extreme paranoia, aggression) so for my health I gave up, because it had me staying awake all the time. I'd do night feeds, obviously, then through the day because they need to feed! So yes, didn't last long. Then with my third, I was SO desperate to give it a real shot but I was told I couldn't because of antibiotics I was on at the time. I wasn't told I could attempt to start breastfeed once I finished them, despite having started her on a bottle. I felt so guilty! Like I had let her down. Obviously in reality this isn't true, these things happen! Anyway, I understand, but your previous experiences won't dictate your future experiences! If you are able to then wonderful, if you aren't then it isn't your fault and you shouldn't beat yourself up about it.
And as far as age gap is concerned don't worry! I can see why you worry, given it was far from easy with your first two, but like you say they have each other now which is wonderful and will be a good distraction for each other while you are caring for a newborn. I have both a huge and tiny age gap between my three, and to be honest the smaller gap I found easier because I was still in the swing of things, it was much less a shock to the system.