Since Mr and Mrs Khan and Abad must be included, we have already chosen 3 people. Therefore, we need to choose 17 more people from the remaining 23 members of the club.

The number of ways to choose 17 people from 23 is given by the combination formula:

\(\binom{23}{17} = \frac{23!}{17!(23-17)!} = \frac{23!}{17!6!}\)

Calculating this gives:

\(\binom{23}{17} = 100947\)

Thus, there are 100947 ways to choose the 20 people.