You can do some really striking designs using just straight lines. I took a class last weekend from Melody Crust on choosing the quilting pattern for a given top. A few things to consider - who the quilt is for, your skill level, and how soon you need it can direct your decision.
I agree that SITD can be harder than free motion, my SITD still jumps out a bit, but I know my 3 year old nephew won't hold that against me.
One other thing that Melody suggested in the class, is when doing diagonals, don't set yourself up to connect all the points unless your piecing is flawless - instead set the seams 1/4 inch to each side - that way if you end up a bit off, your seams can still be straight and it won't be as noticeable. She also suggests edge to edge designs for kids quilts to reduce the number of stops and starts - and that way the ends of the seams can be buried in the binding.
As a beginning quilter myself, I am taking her advice to heart, especially on the two quilts I need to finish before Memorial Day weekend.
Have fun, I'm sure your daughter will love it.
Cheers, K