Binomial coefficients for young kids

I was asked this question un one of the interview about how will you teach binomial theorem to very young students. So i decided to teach my 7th and 8th graders. I started with pascal triangle and then introduced the expansion of (a+b)^n and then showed them the meaning of coefficients in context of finding probability of binomial distribution and they all picked up in 1 class period.
The picture shows the solution to a problem when 13 coins are thrown and they had to find the probability of exactly 6 heads.