This one was always a tricky one for me, trying to create an email to a bunch of people in a friendly manner without using 'hey guys.' It the phrase that feels the most natural to me when speaking to group of people. I personally have always views 'guys' as inclusive of anyone, but I get others may not.

Professionally I have opted to use 'hey all' in 90% of situations because it's about as neutral as you can get. Doesn't feel as natural to me but then I don't run the risk of offending anyone.