I think that for most children, the fabric itself is far more important than the design. Fancy and intricate design is just not important to a little kid.
A fabric that is fascinating is wonderful. They love themed stuff or something that they like like food (say for the teenager) or dolls or pink or whatever, for the little girls.
They would go wild about stuff like that and they'd feel very, very special. They could be simple blocks, but if they were the themes that they love, whether Mickey or Barbie or dolls or pizza, they'd be thrilled, I'm sure.
Fancy patterns, however...don't expect them to be too excited about them. I mean, they will like them because someone made them for them, but they will love them MORE if the theme is what they love as well.
Wish I could help. I love doing the kids' stuff, but I've got a bunch to finish up here...79 in fact, but they will all be tied, not quilted.