We experimented with a lot of different things for our infant son. Our best success was when we put regular adult size Lightspeeds on his head with a soft book or two between his head and the headband to make it fit.
You can get a soft version of the already great big and soft ear seals for those headsets. You can also plug in audio feed for any entertainment gadget you might want directly in to the ANR box. That way, you won't have to listen to Barney yourself, which is important to flight safety.
They’re comfortable and he was happy. Mom was happy because he had the benefit of ANR. I’m happy because he's still wearing them and can wear them for the rest of his life (probably not much of a stretch considering Lightspeed has the best customer service I’ve ever experienced from anyone on anything.)
Of course, we all grew up with lap belts (maybe), no helmets for anything except football (maybe) and plain old passive headsets. My wife thinks I must have some hearing loss because I often have trouble hearing her. There might even be some truth to that.
CAVU