I did something similar in that I had my sim go to each pre-made household town by town and get pregnant by each male sim - She made it to San Myshuno before I stopped and I forgot the count. I had aging off and used the birthday cakes. When the child moved out, I moved them into the house with their father to keep track of them all. I think I still have that file but with the way Sims 4 files are saved you can never tell which is which. It was fun and I moved her to a new town after she 'completed' a neighborhood!
I'm still working on my aspiration challenge and am finally working on the last family aspiration. It kind of messed up my plans for my sim when he would be finished so I'm just wanting to wrap him up and move on. I will redo that challenge again but looking for something new after.
So you are not allowing any aspiration awards at all? I'd probably just outlaw the ones that affect sim needs but keep the others optional! I'm not sure I can deal without a few of those rewards!!
Good luck on this one and I like the relaxed approach - Keep posting - I like the ABC order that you are giving your sim babies!