Being a parent in a big city, the positive thing is that you can choose from plenty of activities that you can do with your kid(s). If your little ones are interested in drawing and creative things in general like my kid, I recommend you try the open art workshop at the National gallery (for kids from 1.5 – cca 5 years).
Each week there is a different main theme based on one particular artist and their particular style or piece of work. Within the 75 minutes of the workshop, you can visit several prepared “working stations” and try to create something. Be prepared: sometimes it can be messy work :-).
The workshop is held on Wednesdays (starting at 15:30) and Thursdays (starting at 10:15 and 15:30) during the school year (closed during school and public holidays). No reservation needed. The entry fee is 60 CZK per person (above 1.5 years). The ticket actually serves at the same time as a same-day entry ticket for most of the exhibitions within the gallery.
Last but not least: if you are in the mood for a coffee or some refreshment, try the spacious Café Jedna, situated in the ground floor of the gallery.