These thematic pictures of Hoạt động are analogous to a visual dictionary. The theme "Hoạt động" splits into several parts. For children, especially toddlers from 1 to 5 years old, it is better to divide the sets of cards over several days, or even weeks, so the information is absorbed better. Especially it is true if you are using flashcards to learn the vietnamese language, which is not your native language.
To expand your vietnamese language vocabulary on the "Hoạt động" topic, flashcards games are the best way: