@jcboy,
I know it's an inconvenience to you, but that little boy Justin will be so happy to be staying with you. One of my daughter's girlfriends also has a somewhat chaotic family situation at home and I've had her staying at our house for up to two weeks once. Yes, it is so much more work, but seeing her happy smile was all that I needed.
It's a darn shame that some kids drew the short stick, but they're just lovable kids and as they said: it takes a village..........
You're both very lovable and generous people and I am glad you're helping Justin. You'll be rewarded, trust me - not necessarily by Justin's mom but I do believe in Karma.