For executive functions, first 5 years are very important, so I wonder that which activities that are beneficial to improve executive functions are suitable?
Hi Vural, here is a reference you can read to understand a bit more about the age-executive function development, it's in spanish but you can translate it online, it mentions a few test that can be used to assess the EF in children, so if you analize what the tests evaluates you can adapt some tasks to favor EF development.
Article Desarrollo de funciones ejecutivas, de la niñez a la juventud
Either way, you can stimulate: inhibitory control, working memory, attention switching, planning. Always considering that some of this processes will not reach optimal levels until later stages of development.