I highly advise you to NOT take them. The subject matter alone should have made you think this would not be a proper thing to do. It's not something I'd ever think about taking any 8 year old two, let alone my niece and nephew.
Go and see it yourself. But IMHO, no one under 18 should see this play no matter how good it is, no matter who is in it.
"TO LOVE ANOTHER PERSON IS TO SEE THE FACE OF GOD"- LES MISERABLES---
"THERE'S A SPECIAL KIND OF PEOPLE KNOWN AS SHOW PEOPLE... WE'RE BORN EVERY NIGHT AT HALF HOUR CALL!"--- CURTAINS