As mentioned by Kallis, there is no such beast as a joint IVA.
Now, as you probably know, if you go into an IVA, your spouse will still be liable for the joint loans in full, so, yes, it is wise that she looks at a debt solution too, as I imagine she wouldn't be able to maintain the repayments on her own. You could look at her going into an IVA as well. These are usually interlocking, which means one I&E and one monthly payment, but don't have to be.
It is possible, on examination of your full situation that one off you goes into an IVA and the other on a DMP, but, on what you have told us, I imagine the two IVA's would be the way.
I would suggest chatting to a couple of firms ( a look around the forum will show you the ones to look for and those to avoid ). I would suggest staying clear of the "IVA Factories" --- over large firms with little regard for individuals.
Best of luck.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014