I'll butt in just for a second.
You and your husband may be one of the only positive influences those kids have in their lives. God Bless You! The river rafting trip sounds wonderful.
Those kids are old enough to know what is going on, and protecting them should be your first priority. I don't often post on other forums besides Substance Abuse, so forgive my naivety in asking whether there might be support groups like there are for Alanon for NA? If so, the kids might be old enough to go there with you, and it may help them to cope with their dad's drug issues. Kids often blame themselves for their parents problems, especially in a separation or divorce situation. They need to know they are not responsible for any of this adult stuff.
You are right, they are getting old enough to move on and you may have less access to them soon. This is your opportunity to cement that bond. They deserve you wonderful people to the extent you can provide yourselves and your home.
FT