I decided to go with Kitchener Stitch for the shoulder seams, since this is a baby sweater and the shoulders won't have to support a lot of weight, and Kitchener Stitch makes the seam look so nice and neat. Here is a close up of the shoulder. Kitchener Stitch is so great because it looks like it was knit in one piece!
Here the whole sweater so far. I have completed the body and started on the sleeves. I'm really liking how quick my progress is on this project!I've noticed that a lot of directions for Kitchener stitch only explain it for stockinette. In that case, with the purl sides together, you want to use your sewing needle to go through the stitches as if to knit the first stitch and purl the second, and for the back needle, purl the first stitch and knit the second. As you go push the first stitch of each set off the working needles. Remember: knit, purl, then purl knit.
For garter stitch it is: knit purl, knit purl - the same thing for the front and back needles. Just make sure the two pieces are facing the right way before you start so you don't end up with two knit rows and two purl rows together.
It's fine if its loose you can go back and neaten up the stitches.