Made a scavenger hunt for my geocaching siblings this christmas

Step one: this present was in the bag - geocaching stickers, magazines (not pictured), log books and so on. For those that don't know geocaching: it's a kind of global scavenger hunt with riddles, mysterious hints, climbing and searching in lost places and lots of looking for GPS coordinates. I decided to send them on an adventure indoors for a change.

The present also contained a tiny, tiny geocache (even an official one - not that easy to get outside the US). I also took all pictures with a potato.

Step two: Inside was a sheet of code. Lots of numbers, some letters in between.

Step three: Interpreting the numbers after H as horizontal lines and the ones after V as vertical rows, we get a puzzle! And if we solve that, we can interpret each block of five pixels as a chain of zeroes and ones, and use the code on the sheet to translate the whole thing into text. If this sounds incredibly hard to find out: they love these kinds of puzzles and we get them in magazines regularly (they recognised the pattern right away).
Anyway, we get a sentence that's the next hint: "Wo gemunkelt wird, da lass dich nieder, Hinweiszettel findest du dort wieder" - thats: "where there's rumors, take a seat; there you'll find the next hint sheet" or something to that effect.

Where are the rumors? On the toilet! It's a family tradition (from my older brothers fiances side) that we adopted - there's a kind of guest book next to the toilet, where family members and guests leave musings or greetings, so you always have something to read there. This particular one was made by my little sister two years ago, I think?

Step four: Inside were two lines of music - guitar tabs and notes. After some playing around on the piano and guitar they were identified quickly: the first line of "Oh Tannenbaum" and "Am Weihnachtsbaum die Lichter brennen" (traditional german seasonal songs, that both mention the christmas tree in their first line). Google tells me that the first one's been translated to "Oh christmas tree", apparently, so you may know it.

... which of course points us here. It was really hard to hide it, because the whole family was in the room all the time. I only drop by for a few hours and the tree gets only put up on christmas eve, so there's not really a choice but enlist my mother to stand in front of it, blocking the view (cue the "your mum" jokes) and showing me the decorations, which I then reach out to touch - well, and place something else there.
The decorations are sparse because cats. Especially one hyperactive young tomcat that destroys everything. Everything!

Step five: Now what's on that tree? A ... screw? Screw you, we were expecting presents!

Wait, there's more ... the screw is also a cache and - wait for it - unscrews! Inside was a QR code, which contained a downloadlink, but that one's an injoke and has no place here.

Thanks for reading and putting up with that piss-poor image quality. We also had no banana on hand, sadly, so you'll have to trust me that this screw's pretty tiny.
Siblings are twins (boy & girl) and 15, btw.