Personally I would just leave the heads alone. Then there is no chance of you getting junk in the combustion chambers and screwing something up. If you have any stuff that is loose then I would use a shop vac to suck it out and leave the rest.
That carbon isn't going anywhere right now, so why disturb it? I'd just clean up the LIM and call it good.
If you aren't aware, pick up the Aluminum LIM gaskets. The replacement ones may be plastic as well and you will be doing this again at some point if those are used.
With that much coolant showing inside the valve covers be sure to wash down the lifters/valley area of the motor before reinstalling the LIM with fresh oil (at least a quart), allowing it to drain back into the pan. Then before you restart the motor, change the oil and use some cheapo oil/filter. Let it run for a few minutes (do NOT drive it, just let it idle), then change the oil again this time using a quality oil and filter. I recommend Wix filters.
Reason being is the coolant is already in the oil and you risk spinning a bearing. I hope that when you get it all back together that it hasn't caused any other damage.
Was the UIM cracked at all? Those are also prone to leaking coolant into the motor.
