It is very cool project, buy I think author (I know, you will read this) take it to the extreme. Again, it is very cool technically, but it contradicts declared goal: to make new computer kit for beginners.
IMHO, it is doesn't matter for novice, what to solder, SOIC8 or SOIC28. SOIC28 is as easy (or hard, if you want) as SOIC8.
And larger chip could make much more useful computer: it will be possible to add some minimal sound (as such chips typically have DAC), keyboard, and, maybe later, true monitor output in VGA style (not DP or HDMI of course).
It will be not much harder (if at all) to solder, but could be good base for expansion if owner gain interest in such things.
IMHO, it is doesn't matter for novice, what to solder, SOIC8 or SOIC28. SOIC28 is as easy (or hard, if you want) as SOIC8.
And larger chip could make much more useful computer: it will be possible to add some minimal sound (as such chips typically have DAC), keyboard, and, maybe later, true monitor output in VGA style (not DP or HDMI of course).
It will be not much harder (if at all) to solder, but could be good base for expansion if owner gain interest in such things.