The PBS Kids website has lots of educational games for kids of all ages. One game I recommend (either playing via white board or mirroring to a physical version in class) is How Tall (PBS Kids, 2015) which is a game about estimation and measuring using non-standard measurement units. It is an interactive game that the child plays with Curious George and the Man in the Yellow Hat (a.k.a. Tim).
In this game, Tim asks the player to choose how many units tall a certain object is (e.g. tree, wooden crate, truck, etc.). This first step requires the player to estimate as they are only given one copy of the unit and 3 numeric choices. After the player chooses their guess, he responds and, if correct, begins to tile the units on top of one another until the final measurement. The game continues until the player measures all of George and Tim’s objects.
Instruction-wise, Tim does a pretty nice job giving clear and descriptive instructions (e.g. “When you are done, click the green arrow”) using a firm, clear voice. This can be helpful for children learning English as a new language as he does not speak too fast and refers to the visual cues. This game is also not too overwhelming with colours, moving objects, and sounds.
While this game encourages children to use unit iteration during their estimating, it may be a challenging feat; especially for children who are just starting to learn about non-standard measurement. One solution would be to take the time to work through the game as a group (via white board for example) and draw out all the units it takes to measure the object before selecting your guess. Another option is to make a cut-out of the shapes used in the game and allow the child to use it to help with their estimation.
PBS Kids. (2015). How Tall? In Curious George. Retrieved from http://pbskids.org/curiousgeorge/games/how_tall/how_tall.html