Here is a great resource to help you reinforce what you are teaching in math.   SoftSchools.com is chock full of fun math games and math worksheets.  They also breaks the games down into categories by grade.  Here I will hightlight just a few that we've enjoyed.

Remember, depending on the curriculum you are using, some games may be too advanced (even if they are a grade or two lower) and others in a particular grade may be too advanced. I don't know how they have determined their grade categories. So be sure to check out the game before your child to be sure they have learned the skills, this will help you avoid frustration or discouragement.

Solve for the Unknown:
Math Lines, Add to 5, 6, 7, 8, 9, or 10
You are given a number on a ball.  Shoot the ball at the number that, when added together, will equal your target number.  I've linked you up to "add to 10."   In the example to the left, the ball in the shooter is number 3, shoot it at the number 7 to equal 10.  Earn points and advance through levels. 

All of the line games are at the top of the page, give them a try!
Read more to explore a few other games.