Here is an activity/game that you can use once you teach commas or at least some of the rules involving commas.
Prepare ahead: Write sentences that need commas on large sentence strips. Make a separate set of commas on smaller and different colored sentence strips, or just make them large, cut-out commas. Using the Post-it brand sentence strips would be great.
Game/Activity: Divide your class into two or three teams. Upon the signal, the first person on each team has to come up to a table, grab a sentence strip and stick or tape it onto the board. Then they grab however many comma they think they need and stick them onto the sentence strip in the proper place. That player's turn is over, the next person on the team repeats.
Ways to award team points:
Have each team's round one player stick up one sentence strip with commas, and you immediately check them to see which team (or teams) earns points for accuracy. It could be one team or all three. Then repeat for player two on each team. When all players have had a turn, check to see how many sentences were punctuated correctly. That will be the team's score.
Give each team an equal number of sentence strips in a pile along with the separate commas. Upon your signal, you'll need to set a timer, each player will find a strip, mount it on the board, and place the comma(s). Immediately, like the relay race, the next player does the same. When one team finishes first, they get a certain number of bonus points. They earn extra points for each correctly inserted comma. They lose points for each incorrect comma placement. Repeat the same scoring for the other teams.
And, of course, the team with the highest score wins!
Hope that makes sense.