I think it would be advisable for you to speak to a professional to get some case specific advice, they will be able to advise at a professional level.
Try wwww.iva.com for a list of companies and some reviews of these, I would suggest you contact 2 or 3 in the first instance to ensure you get impartial advice. x
IVA final payment left the bank on the 26th January 2013...looking forward to a debt free future.
It might be possible to write this kind of thing into your proposal, but you need to speak to an IP.
As Lesley says, IVA.com is a good place to compare a few of the popular companies. Give a couple a call, tell them your exact situation and they'll talk you through your options.
To answer your specific question, the mortgage payments are a priority payment and you will need to keep paying these in order to protect your property. Are the children living with you, or does your query relate to maintenance you may be paying for another property?