NEED HELP!.

My boyfriend of 7 years admitted last night he was addicted to heroin!!!! I had no idea, he has been smoking it for nearly 3 years, £50 a day at his highest and now down to £20 a day. Im absolutely crushed. We have 2 beautiful children age 5 and 15. How could he think it was abit of fun at first. He has decided he really wants to stop, but has only told me nobody else knows and he wants it to stay that way. How can i possibly deal with this burden alone? we are going to a treatment centre today, but im scared....how can he detox at home with my kids about! I dont need them being bought into this or even have to see it!!
just need some advice please on what to expect.