what def to stop this?

I would say, as a former defensive back, that if you don't get pressure on the QB than they will chew you up. I would target man to man bump and run and then have either 2 deep or 1 deep over coverage.

From there you have to blitz and get at the QB quickly. They can't hold the man coverage long. You have 6 or 7 to rush against the O and that should give you one man free all the time. If you vary the blitzing, sometimes from the inside, sometimes from the side and sometimes from the man covering the slot (with a S who picks up that "hot" receiver) than you should be able to get enough pressure on him and confuse the offensive line to get some sacks.

These are 11 and 12 boys and I would imagine the line is not sophisticated enough to pick up multiple blitzing schemes. This is in essence the way the 46 became famous and I think you are going to have to take some risks to beat this team, force some picks and fumbles.

If you don't win, you are just another notch in the belt, but if you stay aggressive and play your plan, you can create havoc for this team. As the saying goes, playing prevent pass defense just "prevents you from winning." Stay aggressive and get your team psyched up about creating chaos. That is what gets defenses juiced up.