@s1h0k Oh looking good so far! The one behind looks younger I think, but the front otter, to me, looks more of an experienced veteran-type warrior. I think what could help is making the eyes a little bigger? That's my first go-to anyway... and a rounder face that's proportionally bigger compared to the body (which could also use some squishiness; google "baby otter", I know you don't want to go to that extreme but it'll give you an idea at just how round they are- also adds to the cute factor, which appeals to the general public so very much - I guess it also depends on your audience). It seems your style is more on the realistic side, so perhaps just pushing it a -touch- more might help?
OH and as for the hat, I think making it oversized would DEFINITELY help make the otter look younger!
P.S. I absolutely adore otters so I'm I super fan of this concept 