Snuggliness is unrelated to the amount of quilting you do (unless you never plan to wash the quilt, in which case it will be stiff from start to finish if quilted heavily). I used to quilt crib quilts far apart believing -- wrongly -- that it was going to make them softer. Once washed, they're no softer or more drape-able than the quilts where I've quilted 1/2-1" apart across the entire quilt. All the far apart quilting lines did was make those early quilts more prone to snapped stitches will all the washing & wear and tear they undergo.
For quilts that are likely to be washed every week or every other week (like most toddler's quilts), they will be sturdiest if quilted at least every 2". I love using Warm & Plush batting. It is fluffy & soft and the little ones love it -- I do too, for that matter. I absolutely wouldn't worry about matching up seams on your quilt, but I would want to make sure it had enough quilting to withstand the rigors young children will put it through. Perhaps in addition to quilting just inside the ditch, you could add another square inside of that.