@Tash that is fun! I'm glad you're making this prompt an opportunity to riff off of something you love. I think you are off to a great start, especially in the sketch where the gryphon is holding its snake tail and waving.
I have some tips for you as you go forward
if you look at the design of the Gryphon you referenced from the Quest for Camelot the repeated triangle shape (in the ears, the green eyes, the general chest shape, and even in legs and wings and beak) make it look really menacing and even evil. another element that makes it work is the variation in size within the design. small head, big chest, bigger wings, small legs. like they guys said (a few times ago when they were critiquing the rock fortress of Jeremy ross) you want to follow the small, medium, really big rule to avoid sizes that are too similar.
I like the really big beak and the small wings you have on your design right now, you could reduce the body size a bit so it is sort of medium to finish out the rule.
also, if you want to make your gryphon sweet you should use a lot of circles and ovals (so a toucan is a great choice, they already have lots of ovals and a happy face). Jaguars are kinda scary, but in the movie zootopia, they made a cuddly jaguar (officer clawhauser) by making him round and soft, so you could do something similar.
see how many circles and ovals you can work into the gryphon, and make the snake as full straight lines and triangles as you can.
I would also recommend doing a few draw-overs of pictures of cats to get the anatomy bits in the right places. Ill add an image of what I mean here later. there is no shame in getting a little help from photo reference! In fact it is a best practice.
@MarcRobinson this is your submission for march? wow I hadnt thought of putting the gryphon into a story, I suppose next month both the boy and they gryphon will show up? that's exciting!
I'm just going to do a few poses on a white background 
