I'm not a professional, but in my observation the penmanship in the samples is, at the very least, right about on target for the typical first grader at this time of year.
The writing is supposed to be large at this stage, because the teachers are telling the students to use two lines, using the one running through the middle as a guide to keep everything straight and roughly uniform in size. That relative uniformity in size, keeping within the lines, maintaining proper word and letter spacing, and proper letter shapes are keys they're looking for. The samples have all of that. The capitalization mistakes are normal, and you can expect your teacher to be correcting and reinforcing that throughout the year. Shakiness is expected because writing is still a laborious process, the students haven't fully committed the letters to muscle memory yet. As long as the shapes of the letters are easily discernible (as they are in the samples), no worries.
First-grade spelling is a disaster in my experience (aka "inventive spelling"), so if your DS is spelling well, he's way ahead on that measure.
