Here is the catch with using iPads, Mathemagician is a flash based site. Thus, you need a different app to use in order to interact with this site. The app we've been using is called Rover.
Safari for the iPad is a better web navigator than Rover so try navigating to the correct website in Safari, then copy the URL and paste it into Rover. This way Rover takes you directly to the game and you are ready to play. You may want to experiment with bookmarking the games into Rover as well.
The creators of Mathemagician (Oswego City School District) also have many other online practice games to choose from. Click here to get to their table of contents. Try playing any of the Speed Grid games, like Speed Grid Multiplication, and see if you can complete their task in the specified time limit. These games are reviewing math facts, but instead of supplying the answer you must determine a problem for a given answer. Another series of games to explore is Stop the Clock, for younger children learning to tell time.