Is this good play, or bad? Or mediocre?

I'm not quite sure. I had a reason for doing what I did on every street, but then it seems like I missed some value in here somewhere. Opponent is completely unknown. My thoughts are added in italics.

***** Hand History for Game 4432601709 *****
$25 NL Texas Hold'em - Saturday, June 03, 17:24:12 ET 2006
Table Table 108079 (No DP) (Real Money)
Seat 5 is the button
Total number of players : 5
Seat 3: luna_mobil ( $22.20 )
Seat 5: Fedtmule777 ( $19.72 )
Seat 6: pigdogpig ( $35.61 )
Seat 2: stressball10 ( $27.60 )
Seat 4: Fly_Fishing_Girl ( $25 )
pigdogpig posts small blind [$0.10].
stressball10 posts big blind [$0.25].
** Dealing down cards **
Dealt to stressball10 [ Ts Th ]
luna_mobil calls [$0.25].
Fly_Fishing_Girl raises [$1.25].
Fedtmule777 folds.
pigdogpig folds.
stressball10 calls [$1]. - Tens are sometimes in my 3-betting range but I have no read to suggest that it's a great idea against this opponent. Readless and out of position I'd rather play a smaller pot.
luna_mobil folds.
** Dealing Flop ** [ 5c, Kd, Ks ]
stressball10 checks. - This is standard for me on this kind of flop against an unknown opponent. Against certain players I might lead but in general I think I'd like to see how they bet this kind of flop - how long they wait and how much they bet.
Fly_Fishing_Girl checks. - She hesitated before checking. Not really the result I want. I'd prefer some kind of bet, frankly, because looks like either a slowplay, or a player who has nothing at all. And neither one stands to give me much return on my tens.
** Dealing Turn ** [ 7d ]
stressball10 checks. - I'm starting to feel like my hand is probably good but it's nagging at me that she could be slowplaying AK/KQ. I think I should have led here. Thoughts?
Fly_Fishing_Girl checks. - Now I know my hand is good; I just don't want to see a face card (except another king) on the river. Not too worried about the two diamonds.
** Dealing River ** [ 4s ]
stressball10 checks. - Here's my other question. Should I just lead here? It's hard to imagine her checking a pocket pair all the way down like this, given the board, so I think she just has AQ/AJ. But if so she played it really cautiously, never betting when she was given every reason to think she could still be ahead. My thought was that she would fold the hands I put her on if I bet $1 or more, but if I checked she might make the same bet trying to knock me off. That's not necessarily an optimal play since her hand has a moderate amount of showdown value on this board, but it's common enough at 25 NL.
Fly_Fishing_Girl checks. - Damn.

Meta commentary: this odd, passive play with high cards that miss is becoming really common at the 25 level, and it's got me thinking. I have historically been very cautious of people that raise pre-flop and then check the flop (especially in position, and even more especially heads up) because c-betting used to be so common, that the absence of it seemed like a trick. Lately it seems like half the raised pots get checked around on the flop, and the first bet from any player takes it down on the turn after that. If I figure that an opponent is playing this passively, should I just value bet whenever the flop looks favorable? It seems like these players will only continue with the hand (calling or raising) when they definitely have me stomped.

Here I think I probably should have checked the flop and then just led the turn. I thought it was 25% likely or less that she was slowplaying. If I had played any similar hands against her later, I would have led the turn every time. I still don't think there was much value betting on the river, but then there was probably little in checking because honestly I didn't have much reason to think she'd bluff at it after the rest of the action.

Final question. I have been mixing it up between 25 and 50 NL recently but I'm a few notches of bankroll away from moving back to 50 permanently... does this kind of thing go on that that level as well? It seems like maybe the general level of aggression on Party's low stakes 6-max games may be declining. I still find plenty of donks and maniacs, but the average players are weirdly robotic - playing a pretty standard TAgg game pre-flop and then check/folding a lot post-flop except when they hit. Sometimes I'm seeing monsters in the shadows that aren't there because I feel like players are checking so much, they HAVE to be slowplaying something.

on the hand i like betting the turn (and folding to a raise) and checking the river, usually folding to a big bet.