What chew toys work best for a two-dog household - Murphy is a 11 year old lab and Coco is a 2 year old Pomeranian?

I am helping my son and his friend buy Christmas gifts for them. They play with them every recess and this is the highlight of their otherwise mundane day. The dogs’ mom said they enjoy chew toys. I figured I’d pull up a list of top chew toys but everything has mixed reviews - too hard and dogs risk cracking dental damage, too soft and you risk choking. What do you all like?