Heya! I have some time on my hands and would be glad to critique Greenleaf ^_^
ART:
Really don't have much to say here - it's really beautiful, the style is quirky and cute, and your usage of colors (especially the balance between warm/cool) is amazing. The lighting's great, the backgrounds are rendered nicely, and everything's really soft and nice to look at. You caught the essence of a children's book really well 
I think the only thing I can recommend right now is to switch up the composition now and then. You have some great establishing shots, but when the characters are talking, usually they stand right next to each other and the camera's placed in front of them.
FLOW:
This is something that sort of jumped out at me, since I also struggle with the same problem. Stuff seems to happen really fast, like one conflict happens and is solved the very next page, where another conflict is introduced. It isn't a pacing problem - I guess it is just a little distracting since I don't have much time to process what just happened and I don't know if it contributed to the plot at all.. Which brings me to the next point: [this particular point is pretty nit picky, but I felt like I needed to bring it up. So please take with a grain of salt..!!]
PLOT:
So far, stuff seems to just happen. I don't think there's any sort of overarching storyline, it's just a comic where characters go on adventures and have fun. And this is fitting for the tone you're going for - you don't need to have a gritty revenge arc if you're just making a lighthearted slice of life comic. I think I would say that Greenleaf is a character-driven comic - but this means that without a plot (or even a main character, as it seems) you really need to step up your characters to make the comic engaging. And that brings me to the neeext point....
CHARACTERS:
So, everyone has their unique personality traits, which I love. Not everyone talks to same (I'm loving how Rufus is the only one that says "mate" so far... British or Australian thing?) I can already label each of the characters with their archetypes pretty easily:
Rufus is the grumpy one with the heart of gold,
Avery is the loveable naive one,
Evlin is the funloving kid,
Nadeen is the stern but loving mother,
and Jonah is the rookie.
And while I love how quirky and different the characters are, I think there needs to be more. None of the characters have any motives, struggles, or fears so far (with the exception of Rufus, who doesn't want to be labelled as a bad guy). I thought Avery's arc was gonna be him trying to find the pin, but it was discovered in the next page!! There hasn't been any conflict or struggle presented yet, either. And makes the series seem a little aimless. I care about these characters because they're cute and loveable, but what are they all about?
[ok I just read the description and realized that Evlin is in fact the main character and there IS going to be a main conflict. I'm assuming that that's when the story will really take off, and the characters' "true personalities" will show. The 16 pages so far are pretty well done because they set the tone, and give a taste of what the characters are like. Hurrahh! ]
An additional note: I don't really know how to say this - make Evlin more SPICY! She's the main character, and the whole story's gonna be held together by her struggles and character arc. What makes her unique? What makes her WEIRD? What are her quirks, exaggerated fears, and motivations? This is something you want to establish before the conflict is introduced and the plot kicks off.
Overall: Greenleaf is really solid, both in art and writing. It's a bit slow so far, since everything's exposition for the time being. I really look forward to what you're gonna do with your characters and story ^_^
