It's Middle English, not Old English (which is otherwise known as Anglo-Saxon). It's not at all difficult (at least that dialect isn't, the one used in "Gawain and the Green Knight" is a lot tougher unless you're from Yorkshire).

Sidgwick and Jackson's collection "Mediaeval English Lyrics" must have outsold Child at least 50 times over. I got my copy when I was about 16 and it was reasonable for Child to assume that anybody serious about poetry could read it.