I don't usually like the name James but for some reason Isaiah James sounds great - strong and masculine and unique and classic all at the same time!
For a girl, I like Isabelle Marie although Isabelle is WAY popular now. Kylie is too girlie and sounds like a nickname instead of a real name (to me). Allison is a classic but is also becoming super popular again - Alli is a cute nickname though (again, very popular). I like Miyah but am wondering about the pronunciation - sounds like Maya? - if so, maybe go with a more traditional spelling or risk your child having to spell her name out forever and everyone fumbling w/the pronunciation. Also, Miyah Marie - are you prepared for her being called M&M (which I personally think is cute but you may not)? If you have time, dedicate a day to each name and say them several times throughout the day in different contexts - see which one feels right. Good luck!
1 more thing to think about - are you going to have another baby? If so, you need to think about will you want an Isabelle and an Isaiah - same 1st initial (well same 1st 3 letters actually) - can be cute; can be annoying depending on how you look at it! :)