I'm a former teacher and I disagree pretty strongly with the paper based on both my experience and on the fact that this paper has been pretty thoroughly gutted by the literature. The more specific you want the knowledge outputs to be, the more guidance you have to give, as a general rule, but inquiry-based approaches lead to something I call "white swan" learning (with apologies/thanks to Taleb). People often find something through the inquiry that they're enthusiastic about learning, and then they continue learning about that long after they've completed whatever was required. It's not something you can plan, and you don't know which or how many kids will find something with which project, but it happens reliably and for each of those kids finding that topic (and the joy and practice of learning something they are interested in in-depth) is far more effective than semesters of "normal" learning.
If you want your students to discover the Newton's second law you are going to have a hard time getting them to do so in a two-hour lab. It took Newton himself considerably longer, and he was actually deeply interested in the problem.
Inquiry does work well, but not without guidance, unless your sole outcome goal is the inquiry process itself. Even at the other end of the spectrum, the Ph.D. candidate or post-doc, things can get pretty miserable if they are poorly mentored.
So while I applaud you for helping develop natural curiosity (but does it stick? That's another question. Do those kids go on to ask more questions like you've started an engine in their minds, or two years later are they just like everybody else...), if you have curricular goals to meet such that their future classes depend on them knowing the content you are supposed to teach, guiding them is much more efficient.
