The Baltics- Looking for Reccomendations

[EuropeanVanderlust]

We are planning a trip to the Baltic States- Estonia, Latvia & Estonia and will also be traveling through Poland. We have done a bunch of research on things we want to see, places we want to hike, etc. Curious what everyone else has experienced on their trips through these countries- any can't miss places/sites/campsites/trails/restaurants/etc?

We will be traveling with our dog- so also any dog-friendly suggestions would be greatly appreciated!
We don't have any real time constraints, so will go wherever the road takes us so to speak!
Thanks in advance!
Diane, Marek & Kona (the dog)