New to TS4... my sims appear to have zero attention span... is this normal?

Probably just the game (my sims do that to me a lot). Try turning autonomy off (it's in the game options menu under 'gameplay') and see if that helps. It could also be partly routing glitches - see if there's objects blocking their way. If nothing else works, try pausing before getting them to do stuff - this gives the action time to load and could help a bit if you have a time limit on what they have to do.
Hope this helps!