Hi DBASam, about a year ago, I went through almost the same upgrade Win2012, SQL 2014 AOAG 2 Replicas to Win2016 SQL 2016.
I ended up getting so guidance from Microsoft to make sure we were going in the right direction.
Consideration # 1 - When you do your failover to your SQL 2017, you will not be able to fail back nor replicate back to the SQL 2014 instance. There is no downgrade possible. Just plan accordingly and make plenty of backups of your SQL 2014 database so you can Come back to the last known good version.
Consideration #2 - When you add a Windows 2016 to a Windows 2012 cluster, the 2016 will be in "Compatibility Mode" there will not be any of the 2016 features. After you've done your failover to the new Replica's on Windows 2016, Before you can upgrade the Cluster to the Native 2016 Cluster, you will need to evict ALL old nodes to be able to upgrade it. To upgrade the cluster, all you do it run this command in Powershell:
Update-ClusterFunctionalLevel -Cluster "ClusterName"
Hope this helps !