Throughout these encounters, you make it clear that to stray off the path in fairyland is very bad news. What sort of troubles would be appropriate to bestow upon PCs who make this mistake? And how far off the path must they go to have calamity befall them? In the Queen Beatrix encounter, it's suggested that just to place a single foot off the path is a bad idea (if it wasn't, why would the PCs insist on not giving way at all?)... what sort of thing should happen?
You also mentioned that you would wirte up a detailed encounter based on a premice given here. If you're still doing that...
I recall a fairytale involving helping some sort of gnome and cutting down trees. Inside one of the trees (a huge, gnarled mass of knots and very hard wood) was a treasure of some sort. I also want the encounter to involve some sort of opposition... a delema, such as a spirit inhabiting the tree which doesn't want them to cut it down. Perhaps another "woodcutter" is also around who wants to cut down the tree... except that the woodcutter is not who he seems to be and is in fact the stereotypical "greedy man (greedy relaton?)" who overheard the gnome's instructions for finding treasure? Something like that.