How can I filter iron out of kiddie pool water?
I have this exact same problem. The only option I have found is to use a chemical additive to precipitate out the the iron and then do lots of filter cartridge changes. Luckily, the cartridges don't seem to be deteriorated by the orange stuff, and you can just swap two of them every 12 hours and wash them off with the garden hose. If you have a full size filter, you will just need to do a backwash every day or two.

It also helps to get in the pool and stir up all the precipitate off the bottom so that it can be captured by the filter...there's nothing in there that will harm you, it's just orange.