Everyone has a sheet like this with numbers 1-6 and then throws the dice on their turn. Cross out the number you get, the one to have crossed out all numbers first has won.
A bit simple for the 4 year old but still happy to play, good training for the almost 3 yo to count how many dots he got and then to find the equivalent number on the paper. Also, he learned surprisingly quickly to recognise the number without counting the dots.
The credits for this game (even though I slightly changed it) goes to the great Swedish crafts blog skapligtenkelt.se.