Since your pH is high-ish, yes, skipping the borax till it comes down would be excellent.

Thank you for stepping up to care for your sister's kids; so many people today expect that 'the government' will take care of it. But, money and foster homes can never replace even a half-functioning family. My family has seen, again and again, the impact of drugs and the lifestyle that goes with them. My wife sees it every year as a 'resource' school teacher, since many of her students have been affected by parents who've made similar choices; my 18 year old son and his girlfriend both currently work with an urban Wyldlife middle school outreach program. He's in weekly personal contact with about a dozen middle school kids affected by drugs. (I'm Facebook friends with some of these kids -- it's fairly disorienting for a 59 year old to get exposed to the social world of those kids!)

But personally, I'd be more than willing to pull the trigger on some of the dealers and gang leaders who've affected youth I've worked with -- I know some want them to have a 'second chance', but I've seen the kids they are destroying, while they are getting their 'second chance'! I had an urban Boy Scout troop that collapsed after I explained to several of the dads (refugee immigrants) that their sons were being forcibly recruited into gangs. Fortunately, 4 of these dads -- even with their very limited financial resources -- moved their whole families to other communities where they could find work, but with a lesser gang presence.