Our twins are now just 13. We have survived so far I believe, because we both accept our roles as parents first and foremost. You may have had the initial desire to have children, but surely at no point did your DH say he didn't want kids - so don't feel guilty about "this is just not what he signed up for". He's a father now, there's no changing or denying that fact.
How is your relationship in terms of communication? Do you make time to talk together, to just chat over a quiet dinner? Could you get your nanny to babysit one evening a month so you can do "date night"? Spend some time and make an effort with each other, make sure you both feel appreciated.
If he doesn't "do stuff" with the kids, then make a list for him to work through of activities that he could do with them. It doesn't have to complicated, trips to the park, walks to feed ducks, painting in the garden etc. Doing more stuff with them will help bring them together, on both sides. Do things all together at first, then give him an hour on his own with the kids, build up his confidence. Your kids and DH need to do fun things together to enjoy being together perhaps.
The first time I went away from DH and kids overnight, I made a detailed timetable for him so he would know when to feed them! He's at work most of the time too so didn't really have a clue about our day time activities etc.
It's not always fun being a parent, and twin toddlers are hard work! But it does get easier in many ways as they grow up 