ABS and PLA are already heavily used in making toys, so they'd be no more dangerous than any other toy on the market.
Except that mechanical strength of the toys is less when 3D printed than when injection moulded and so pieces are more likely to break off when chewed?
The problem is the voids - tiny gaps in the 3d printed layers provide nice reservoirs for bacteria growth.
I'm sure this will have an age range of like 8 years old and up where chewing on random things is less of a problem.