That's a great idea for the language. It really give you a feel for how strange everything must seem to him, but at the same time it's nice to know what they're actually saying.
Is there a perspective problem, or is that guy huge? Didn't you say Zephonith was around 5'11"? This guy looks like he's bigger than Partasah. Or maybe I'm just dumb when it comes to height. I'm 5'1", so most people fall into the general category of "a lot taller than me."
Have fun with your Assorted Christmas Family Stuff!