Dee, the AoPS online courses can move pretty fast, but if you do the book on your own with your kids, you can take as much time as you need. The pre-algebra text is pretty comprehensive, so you don't need to know a lot going in. But you do need to take the time to do ALL the problems if you want to get full value. There's almost no repetition in the AoPS questions; each requires a new bit of thinking and is worth doing.