Some online shooting games that are appropriate for kids are "Rambo Bros," "Burst the Pig Balloons" and "Feed the Crocodile." These are free to play and family-friendly.
"Rambo Bros" is a kid-friendly shooting game that involves Mario and Luigi shooting their enemies.
In "Burst the Pig Balloons," the player uses his gun to burst pig-shaped balloons. This game, which is appropriate for kids of all ages, only uses the mouse for shooting the balloons.
"Feed the Crocodile" is a game in which the player is an elephant that is friends with a crocodile. The elephant, Ellie, helps feed her crocodile friend oranges by shooting them into his mouth.