Garments with buttons / buttonholes can be a little bit frustrating as you try to mark the positions of the buttonholes.  The easiest sewing tool I've found for this purpose is the "expanding gauge".  Open the gauge so that the points are the correct distance apart, then mark the positions for the buttonholes.

This same tool can also be used for marking pleats as well as other craft items where you need to mark the distances between decorations, appliques, initials, etc.

And, speaking of buttons, nothing is written in stone that says you HAVE to sew four hole buttons a certain way.  Especially in children's clothing, try sewing them on "decorator" fashion, as in the examples below.

OR, for more of a "decorator" style, try using a variety of assorted buttons for closures, or try spacing them together in groups or two or three instead of the standard even spacing down the front.

In sewing you can "bend the rules" a little, expecially when sewing for children, so try something a little different - you might be starting a new trend!