Hi there,
The sample size for a mortality survey and anthropometric survey conducted within the same sampling frame will always, except in the rarest of occasions, have a different sample size. If the sample size calculations are similar for the mortality survey and anthropometric survey simply choose the larger number and conduct the mortality survey at all selected households and the anthropometric survey at all selected households that contain 6-59 month children.
If the sample size calculations are very different, for example the mortality survey sample size calculation is twice the size of the anthropometric calculation, conduct the mortality survey at every randomly selected household and conduct the anthropometric survey at every second household.