Is pedophilia a sexual orientation or a mental disorder?
Before trying to give any sort of answer, it is important to address a common misconception. In popular culture, the terms child-molester and pedophile are often equated. Scientifically, they are not at all the same. The approximate scientific definition for a pedophile is:


  an individual that has an unwavering sexual attraction to prepubescent children similar to attraction heterosexual men have for women


This means that a pedophile might or might not molest children, and a child-molester might or might not be a pedophile. Further, implicit in this definition is a close resemblance to a sexual orientation, and if you want a through and careful discussion of this (much better than my answer) then read:


  Seto, M.C (2012) Is Pedophilia a Sexual Orientation? Archives of Sexual Behavior 41(1): 231-236.


Now, the actually relevant scientific discussion (as opposed to merely a semantic distinction) is threefold: (1) can pedophilia be considered a choice in the legal sense? (2) what causes it? (3) can it be treated?

Note that for what we typically consider sexual orientations, questions (1) and (3) have clear answers: no, and no. However, for mental disorders, all permutations of answers to (1) and (3) are possible. Thus, answering these questions does not let you clear up semantic ambiguity.

To start with question (2): in broad strokes Blanchard, et al. (1999) and Cantor, et al. (2004) suggest that pedophilia has a prenatal cause. For question (3) there has been no evidence to suggest that pedophilia can be treated or "cured", much like how you cannot "cure" homosexuality. This lead to Van Gijseghem expert testimony before the Canadian Parliment's Standing Committee on Justice and Human Rights that you quote from in your question. He concludes that pedophilia cannot be 'cured' through penal intervention. However, it is possible for a pedophile to abstain from becoming a child-molester. 

This leaves us question (1), the legal part of this. In Canada, being a pedophile is not a crime, but molesting children is a crime. The status of pedophilia as a mental disorder or sexual orientation is irrelevant to this since both mental status and sexual orientation are protected by Canadian law as long as they do not infringe on other's rights.  To help pedophiles abstain from molesting children there is the Circles of Support and Accountability (CoSA) program (note: it deals with all kinds of sexual offenders, not just child-molesters). This program is aimed to manage and not 'cure'. Wilson et al. (2007, 2009) have shown that CoSA produces dramatic decrease in re-offence rates for sexual offenders.