Keeping different parts of music going in a group is difficult for a lot of people, but it is essential as a budding musician because everyone has their part to play. A drummer cannot start playing with a guitarist, and the singer can't start humming the bass line.
Take a look at this, and beat boxing in general. Biz Markie has a small segment on Yo Gabba Gabba that you can look up on YouTube. Show the kids, and then work on your own beat!
If you are a sophisticated app user, there is an app called Loopy. Jimmy Fallon has used it on his show, and it lets you lay down tracks. Might be really fun to try! (I will try it this fall with my music class and let you know how it goes.) You can see Jimmy Fallon use Loopy with Billy Joel, and he beat boxes with Will Smith, too! (YouTube is your friend here.)