I think honoring the grandmothers is important but maybe you should try to work it in as a middle name.
I'd view Everly as 'made up' rather than 'unique'. The problem I have with made up names is that I read them as surnames, especially when they're paired with traditional names as middles which they invariably are. For example, I'd look at Everly Noelle and see 'EVERLY, Noelle' as if the name had appeared on a register surname first. Therefore I shopped around for some other options based on the 'Eve' parts of Beverley and Evelyn and came up with these:
With the exception of Maeve - possibly - I believe all of these could be considered unique right now. I particularly like Lieve Noelle and Everilda Ivy.
Everly is my favorite girls name! The NN Ever really won me over.
I understand that it does sound quite trendy so if it's something that you want to avoid then I wouldn't use Everly. But if it doesn't bother you then I say go for it.
Everly Noelle is beautiful. I also like the suggestions of Everly Snow and Everly Winter.
I think Scarlet is more popular than Everly, so go with Everly. (plus it honors family, which is always a bonus) The idea of Everly Ivy is nice, but to be honest it's rather a mouthfull. Everly Noelle is beautiful. I also think it may be beneficial to consider a snowboarding related middle, like previous posters suggested. Winter and Snow are ideal ones, and they sound good with Everly. I like your other kids' names by the way!