Hi Rebecca,
You certainly have a lot on your plate there.

I just wanted to mention to you that "mouth opening" can be a tic. Not sure it's that "unusual".

The 3rd video down shows more clearly that it is more of a yawn (as in: drawing in air) than just opening of the mouth but I've seen yawing tics before.

I just wanted to leave you this link from Leslie Packer's site. I personally would advise that you show no more attention to your son about this yawning or blinking. I'd just ignore it actually. With more tests coming up soon you'll hopefully get more answers. Now you have the videos on record, it might be a good idea to just let him be for a while and see how he does.

Anyway, in the meantime, here's a List of Common Tics from what I think is a good source.
http://www.tourettesyndrome.net/wp-c...CommonTics.pdf

All the best to him and to you in your endeavours to find information to help your family.

you take care of YOU too hey?

Edited to add: Just also wanted to mention that a lot of children around the age of 4 have a transient tic. There are a number of conditions which involve tics. Simple childhood tics or transient tics usually disappear over several months.

Tics can sometimes be internal although I'm not sure if there was any Diaphragm involvement during his surgeries and whether that could be causing some sort of "irritation"?

You're doing the right thing by having him checked for seizures.