Re: Knowledge/Perception Checks
Generally speaking, I prefer to make knowledge and skill checks on behalf of the players . . . rest assured this is not a trust issue at all, I see it as an issue of game flow and immersion.
If you'll describe what you wish to do I'll decide which skill is most appropriate for your description, assign modifiers based on that same description, and make the check. This just seems to me to keep the story flowing and puts mechanics in the background, making for a more 'organic' feel.
I also use the 'Passive Perception' mechanic - any time your characters are in a situation in which they would naturally be wary (such as your pending trip into the Puddles) I assume they are taking 10 on Perception as a matter of course. Any time you'd like me to actually roll a check you can cue that with a simple statement about looking for something (e.g. "Larissa looks around warily, trying to make sure that nothing is lurking in the shadows.")
Also, I'm quite aware of my shortcomings - I'm getting old and forgetful. So if you think I'm forgetting something or shorting your character somehow, please check me on it. It's not intentional (unless there's a valid story/rules reason for it) and I won't take offense at being questioned!
