Illustrations for English learning titles at primary level

These English-Chinese learning books target at children whose English are at primary level. The purpose of drawing illustrations is to help the English learners to understand relevant grammar points.
I need about 30 - 40 illustrations for each title. There are six books in this series for the time being.
I am now considering creating two characters (animals or human beings), one male and one female, for all 6 books in the series.
My plan is that 20 illustrations are spot illustrations which are about the size of a quarter page (1/4). And 10 illustrations with the two characters which are also about the size of a quarter page (1/4).
Our target timeline for the completion of all 6 books is 30 April, 2020. Illustrations can be completed in batches.  As this is an English learning book series, the main purpose of the illustrations is to help the books look more interesting.
The target readers are primary students and their parents. It is important for the primary students to find the books not so boring first and motivate them a little more to learn grammar rules. I need illustrations  which have a touch of humour.