Tracking giants

Leaving the orc lair, following any directions they may have gathered there (either from coercion or searching the lair), the party begins their trek across country toward a fire giant stronghold. The giant stronghold is deeper in the mountains, on the far side of the river, overlooking the fetid reek of the volcanic swamp.
The way there is difficult, although Imogene is able to locate a usable trail leading toward the stronghold. Travel is slow, but by the middle of the next day, you can reach the river. Towering over the cliff on the far side is an old keep, crumbling in places. You have the advantage of a sheltered view, and can see that the trail leads down to a shaky rope and wooden bridge stretching across the river. The river is narrow and quick here, and the bridge looks like it has not been used regularly in ages, although there are recent, rough repairs (survival DC12 suggest the orcs use the bridge, but the fire giants can leap the gap).
Access to the stronghold from this point is for the orcs' use. The giants don't bother with any watch or guards, not really fearing anything attacking them. The orcs use this trail, the bridge, and a trail on the far side winding up to the base of a small tower at one corner of the keep. The keep is a small box keep at the top of a sharp drop, with a tower on one corner running a floor higher than the keep, and built down the cliff two stories. There is a light coming from the door at the base of the tower, and two orcs stationed there. They are not paying the least attention to anything going on.
There are three traps set up in this run. The first is a trip wire on the near side of the bridge, which causes a loosely braced pile of rocks to clatter down. The trap can be noticed with a passive perception of 15, or when actively sought on a DC12. There is no need to disarm it if noticed, it can be avoided. Setting off the trap causes the rocks to cascade down. Characters need to make a Dex ST at DC15, or take 2d4 damage. This will alert the two guards, who begin paying attention, though they remain at the gate.
The second trap is on the bridge itself (perception DC18 to notice), which has several places where hasty repairs have been made. One of these is for show, and will cause part of the bridge to collapse under the character. Have them make a DC16 ST using athletics or acrobatics, or slip through the bridge. If someone fails by greater than 5 on their roll, they fall through the bridge onto the rocks below for 2d10 damage. Someone catching themselves on the bridge can be helped out. Players can climb up from the canyon below at half speed. This trap brings the two orc guards out along the trail toward the bridge to investigate. They will come far enough to see the characters, but will stop short of the third trap, watching and taunting as the players draw closer, trying to draw them into the trap.
The third trap is located a third of the way from the bridge to the tower, with another trip wire concealed near a small gap in the rock walls. There is a log drawn back that will slam into anyone tripping the line. The trip wire is noticeable on DC15 perception, and the ram slams the character for 1d10 bludgeoning damage on a failed DC18 Dex ST.
After this is set off, the two orcs charge.