Right from the off we were told our 9 wk old pups could have chicken wings, which they get practically every day (I cut the wings into 3 pieces so they're only get a third each time)... they absolutely love them, for the next 30 mins all you can hear are two sets of jaws going chew-chew-chew. Given wings only cost $3 a kilo at our local butcher there's no excuse not too.
The other type of bone we were recommended were cooked Lamb Shank bones... obviously being smoother and so hard no set of Maltese Shih-Tzu jaws could chew right through them, hence they'd be safe. Unfortunately my partner hates lamb so I don't reckon the boys will be getting any soon :-(