Try to do daily, or about 3 times a week, sight reading exercises of some kind. Even if itís something you write out on your own on a music writing program or Musescore then just transpose for all instruments. I did one key at a time to build consistency.
Always remind each instrument of the notes to watch out for. Tell them the fingerings. Itís as much practice for them as it is for you. Always pretend youíre in the sight reading room and run through the process. You donít have to do the entire 7 minutes, but enough for you and them to get the practice in.
I also used the Foundations for Superior Performance book to practice the scale exercises. Thatís all sight reading is: scale exercises. Theyíll be confident in doing them from the book, and when they see them in music theyíll recognize them. Start incorporating all these things on Monday, one or two at a time. SR preparation is like preparing for a marathon. Itís not done in a few weeks. It takes months, especially for a young group. Best of luck!