Hi there...
My therapist said that since bi-polar "runs" in my family, I most likely have a type of bi=polar, but mine focuses on the depressive end of it.
I started prozac (generic) and my moods shot sky-high... I had a huge upswing, and my doc decided I also should have a mood stabilizer - this helps keep my highs and lows at a more manageable and livable rate... I still have good and bad days, but they're "normal" not extreme.
I know here in missouri there is a group called "grandparents as parents" through the state assistance program, perhaps there is one where you live - the state can at least lead you in a direction... Raising children is hard enough - but you're raising grandchildren. At this point in your life i'm sure you were looking towards retirement and having the grandkids visit at holidays & birthdays....
Of course you're stressed, and rightly so!
If you can find a therapist, i'd say go for it. And kudos to your husband for being on your side and supporting you.
Maybe the whole family can get into therapy, even a few meetings can help.. Good luck.