As for batting...
Most battings are amenable to machine quilting, but some are pretty much strictly for hand quilting. The most common ones you will see are cotton or polyester or a blend of the two. For a baby quilt, polyester is the best way to go.
"Loft" is how thick the batting is. High loft is best tied and lower loft, quilted (or maybe tied, I think). Make sure you check to see what the particular batting recommends and abide by that.
When you kids were infants, a friend showed me a baby quilt that her friend had made for her. After she washed it, all the batting had clumped to one side. It was not repairable. The maker had used a batting that wasn't "bonded" and had tied it, not quilted it. The batting acted like polyester fiberfil. clumped together, and the quilt looked like a huge understuffed pillow.
"Bonding" is a treatment (can be chemical or mechanical) that makes the batting stick together. Sometimes they fuse it, sometimes needlepunch it. At any rate, I ALWAYS look for "bonded" on the instructions. And then, I also ALWAYS look to see how they recommend holding the sandwich together. Most times they will tell you to "quilt x inches apart". (Often it's something like 3-4"apart.) Ballpark is good on this: 3-4" is about the distance across my fist. Machine quilting is always a good way to go with baby/kid quilts, but tying is OK too. (Again, I would check the package instructions and still run a quilting line in the ditch along the outermost border if you tie.) For tying I would be pretty generous (in fact, 3-4 inches may also refer to tying, not sure) and you can have the knots on either side of the quilt...whichever looks best. When tying, I will take 2 stitches (down stitch and then up about 1/4" apart and then another in the same place) and them triple knot (square knot type) to make sure it stays in place. You can even put a little drop of "Fray Check" on the knot to be extra cautious. (Fray check is runny so try it out on something else before you use it on a quilt!!) NEVER put buttons, bells, or anything else a kid could bite off on a quilt, meant for a child!!! As I said before, double check every seam to make sure you have sewn it with enough seam allowance on both sides, make sure everything is secure and triple check that you have taken ALL the pins out before you give the quilt up.
Making sure the seams are secure and the allowances are big enough is important. On the red white and blue guest bed quilt I made in Germany I had to do some extra work on a seam that was coming out (too little seam allowance) when it was on the frame being quilted. Not an easy thing to do at that point!!
That's about all for now...I hope this helps!