I've taught to a group and I've taught my own kids. My 6yo struggles from the standpoint that her fingers are so much smaller than, say, an 8yo's or 10yo's, so it's harder for her to cover the holes well and completely. Also, she has to stretch her fingers more.
I used a variety of materials. Much is available online -- there are even online tutorials for fingering and stance. As Lucie said, I wouldn't just plop a child in front of the computer, hand them a recorder, and announce, "Okay, here, figure it out."
For my purposes, it made the most sense to demonstrate what I wanted the child to do. For example, I might show the fingering for G, then we practiced that; then we tried A, then B. And, in the group setting, I divvied everyone up into 3 groups of one note each (G,A or B), pointed to them in turn, and had them play Mary Had a Little Lamb. It was fun.
I noticed that some kids are able to play by ear once you point them in the right direction. I'm like that, and was surprised to find that others weren't, quite frankly. Some do best when they memorize everything you do, and play by finger/tone memory. And some enjoy learning to read music and learning to count the beats. In any event, don't be too surprised to discover your child takes to music a different way than you do.
I liked Penny Gardner's
Nine Note Recorder Method for the music, but I thought the way it taught the notes wasn't the best, and I downright disagreed with some of the fingering (there are various ways to finger various notes, as you'll discover in group lessons). Of course, it only teaches 9 notes, so you miss out on a lot of music!
I learned from the Trapp family's book of recorder, which is currently who-knows-where (we're painting the living room right now, so everything's in an uproar) so I can't give you the complete title. I liked the variety of music in it. Lots of duets.
Most beginning recorder books seem to have pretty much the same tunes in them.
We have 2 plastic Yamaha recorders. Very nice. We also have a couple of cheapo plastic ones that are hard to play in the upper and lower ranges. I also used to have a pearwood soprano. Wood is harder to care for, and varies more in tone.