I've never lead a walk for a group of kids, but i can share some ideas that helped me get my grand kids hooked: before you start your walk, show the kids pictures of what they can expect to see -- maybe even get them competing on who finds what first. this has nothing to do with actual birding, but a game my 8 yr old grandson loves is "guess what bird i'm thinking of". The guessers ask questions about size, color, location, etc. to get clues. also, point out sounds to them: my 3 yr old grand knows when her cardinal calls, and loves the idea that cat birds sound like cats. Have fun!!!