Yes, you do need to add the bleach now, even if you know it's going to "leave"--if there's no chlorine in the pool, it's not sanitary for kids to swim in it. In fact, you really need to keep adding as necessary to maintain the 6 ppm for as long as they'll be in it.

Draining and refilling over the weekend is a good way to go....then adjust your shock level according to the table and shock at least through the end of the weekend. I wouldn't wait any longer than that to shock it, though--if the chlorine demand is that high now, whatever you've got waiting to bloom may get a step ahead of you and then be harder to kill off.

And no, your questions are not stupid--I'd much rather you know what to do now, than wait until your pool is pea green soup and THEN try to clear it up!!
(It can be done, but I'm glad you're heading off the problem before it gets that bad)

Janet