Unfortunately, they're too suspicious to step into the light themselves (for now), though they probably won't be able to hold back all of the lighbulbs if they make a break for it.

They will, however, scribble a note on a piece of paper (something like, "This comes from the Silent Mountain, if you find it give it to someone who works in the Research Center, we'll be in contact" or to that extent. Most likely it'll be in Levi's handwriting, at least past the first few words when he notices Hange scrawling in their unreadable script and snatches the note from them) and wrap it around a rock before tossing it in, as well.

While this will (eventually) reveal to them what the light does, chances are they won't hear from Erwin whoever the note and peach end up with until they're back.

So after taking some notes and marking the area in whatever little map of the place they're drawing, they'll be heading back to whatever transport they used on the way here and heading home.

They'll be reporting their findings to Helene again.