Aeroplanes are as safe as their maintenance, whether they are one year old or 80 years old. The aeroplanes you've listed there are very common training aeroplanes found just about everywhere in the western world, and whilst not new, all absolutely fine for any level of training, if they are maintained well.
And realistically if they weren't maintained well, they'd probably have been grounded thirty years ago.
Personally (I am an instructor and have flown all of those types), I'd pick the C152 as the best for PPL training, then if he goes on to advanced training the Aspen C172. But none of them are bad. The PA28-180 and C150 are the most elderly and may have less modern cockpits, so would be my last choice, but still fine.
I'd not worry.
G