Yes, you can.
You can attempt to Bull Rush the target of your charge, instead of making an attack. This bull rush allows you to activate your Squash Flat feat:
Whenever you make a bull rush attack and your check exceeds the target’s CMD by 5 or more, you can choose to expend one of the increments of 5 feet you would normally move the target back to instead attempt to trip the target as a part of your bull rush action.
Assuming you beat the target's CMD by 5 or more, then you automatically gain an attempt to Trip your target. If this trip succeeds, and you are unarmed and your target is your size or smaller, then you immediately can spend a Swift Action to activate the Spinning Throw feat:
On a successful unarmed trip combat maneuver against an opponent your size or smaller, you can spend a swift action to attempt a bull rush combat maneuver against that opponent. If your bull rush succeeds, you can move that opponent to any unoccupied square you threaten, then push that opponent the number of 5-foot increments your successful bull rush allows. The target is then knocked prone. If the bull rush fails, you can use the Ki Throw feat as normal. If you also have the Improved Ki Throw feat, a successful bull rush allows you to push the opponent into a space secondary targets occupy. You resolve this effect as if you used the Improved Ki Throw feat to throw the opponent into that space.
Technically, you could even use this second bull rush to make another trip attempt with Squash Flat, but your target is already prone, so the maneuver would fail. But if the ability triggered a different maneuver, like disarm, it would be valid.
Just remember that to attempt a maneuver, the target must be within your reach. If you bull rush a target 10 feet away, how will you trip him if your reach is only 5 feet? You would have to find a way to increase your reach first.