-Play card and dice games with them.
-Practice counting forward and backwards by 1s, 2,s 5s, 10s. Try starting at a number other than 1 sometimes.
-Work with them on partners of 10. (2+8, 7+3, etc.)
-When they are adding/subtracting encourage the use of math tools (120s chart, number rack, etc.)
This link has many printable resources/manipulatives to help your child with math.