Searching for a Fantasy Film

A long time ago I watched a fantasy/family movie and I can't remember the title. I remember very scant details, some quite fuzzy, because frankly, it was kind of a forgettable movie. What can I say? I was bored. Forgettable though it was, I keep trying to remember it and not remembering the title is driving me mental. So, here's what I've got...

Father and child (son, I *think*) move to some remote location, lots of woods.
I'm pretty sure the dad is a surveyor - uses one of those surveyor tripod thingies (only pretty sure).
They stay with a stepmother and stepdaughter. Or, at least these two own the woods.
The stepmother is the bad guy.
The stepdaughter is blind and magical.
I think unicorns or a unicorn are involved.
The movie does the thing where the dad gets a little book as a gift (from the blind girl?) and then later on it saves his life when an arrow or something gets stopped by the book.

The real kicker is that I so vaguely remember the film that I'm only half-confident of a couple of even those scant puzzle pieces. It was hardly a legendary film, cult classic, whatever - it was just kind of a bad film to my recollection, so I assume it's really forgotten.

Anybody want to help me crack this one?

PS
It would have been made in the late '80s, but probably more likely early to mid '90s.