1. For quiet play for individuals, give each child several baggies each one marked with a number on it. (I like to start at 3 and then go higher maybe to 10 depending on the level of the children in the class.) Then give them a bag of cotton balls(ping pong balls, anything small enough to fit) and ask them to fill the bags with the correct number of cotton balls as the number on the bag.
2. Take the class on a type of scavenger hunt through the classroom. Start with trying to find out how many shoes are in the room, then go to how many jackets are in the room, windows, etc. Children could be divided into teams and limited to certain areas of the room to make it more manageable.
3. Use the game of Simon Says to help with counting. Simon will give commands to do do things a given number of times--such as "Simon Says, Clap your hands 4 times." This can go on for a long time and the kids love it!
All the things you do throughout the day can be opportunities to learn numbers! Repetition that is fun is what makes learning fun for this age.