I think you've made yourself clear that you don't want the boys to go with people they don't know. Leave it alone. IF he asks again I would take the previous advice and say something along the lines of "I have it covered, thanks" you can add a "thanks for checking and/or have a nice trip" if you want.

Me-44 (45)
H- 50 (51)
M-'96

S-18(20)D-15(17)D-12(14)

BD Feb 2014 (he works overseas)
home Oct(sep rooms)
(EAs possible Pa's unconfirmed)
insists wants D through July 2015
no more talk of D since