The attack from the Steadfast Boots is not an AoO, just like the attack you ready when setting your weapon against a charge is not an AoO. Taking an action you readied isn't even an Immediate action, as far as I know, so yes, you can use your boots as often as you want, assuming your enemies don't figure out that charging you is a Bad Idea.
In fact, when wielding a reach weapon, you can take the attack provided by your Steadfast Boots when they enter your threatened square, then take your AoO when they try to keep charging and leave that square, if the double damage attack didn't take them out already.