I don't have twins, but there is only 11.5 months between my two, and they were two and three when my husband left after having an affair (with their child minder!).
I had just got in the police, and got a start date 4 months later. I had to go away to police training college for 15 weeks with only weekends at home.
The kids had a combination of nursery and child minder, then they stayed with their dad at his parents house in the week. They adapted to this fine.
I actually relished the time away (although of course I missed them). With what had happened I think it was actually perfect timing, and it allowed me a bit of time and space to be me first, rather than having to be mum first.
I suppose what I'm getting at is that actually, the smaller they are, the easier they adapt. I've always worked, and they've been through a fair few childminders, nurseries, holiday schemes etc. They thrived at nursery etc, and it meant I could work knowing they were well looked after. It also meant I appreciated the time I had with them more.
It's not easy, there is times when I've been lonely, when ive been stuck for childcare whilst doing shift work, and when ive got angry that my ex got to swan off, start a new life, and not have any of the responsibility. However, I wouldn't be without my kids for the world and they've grown into happy, well adjusted teenagers.
As for my ex, I look back and see he actually did me a massive favour as he is not a very nice human being and I'm glad im not stuck with him! Some of the stunts he has pulled over the last 14 years would make your hair curl and sadly, whilst the kids love him, they know exactly how far down his list of priorities they come.
I think going back to work is a great idea, both for you and the twins. You've been so strong so far and are doing brilliantly!