There is no need to "play devil's advocate" - if you believe something, argue for it. If you don't believe something but think I'm missing something, you can point it out and make a case for why it's important without being confusing about what you actually believe.
All evidence I have seen is that Hamas does not systematically use child soldiers. We can see the indiscriminate tactics of the IDF; we can put that together with the high death toll to make a reasonable conclusion that vast numbers of civilians have been killed. You're trying to cast doubt on this idea but the amount of doubt is akin to flicking water from your fingers onto a housefire.