Attention spans are short. Here is the "Wake em Up" way to keept the audience with you. After you have created your talk, go through it and make sure that every 2-4 minutes you use some kind of attention gaining device.
You could increase your voice inflection, show a visual, hold up a prop, move around the room, tell a story, throw out a one liner, write on a flip chart, show a picture of your kids if you want to. Just make sure that no more than a few minutes goes by between attention gaining devices. The audience won't know you are using a technique on them, but at the end they will say. Wow! That time sure went by fast!