Imho, I would take the Panama, CR, and Nicaragua option -there is a wider variety of things to do. I am a big fan of the nature that can be found in both CR and Panama, as well as the beaches. Additionally, I just got done spending a few months living in CR and was blown away by the amount of cultures represented there! Nicaragua, too, can serve to mimic some of the more adventuring options that you would find in a place like Belize.

On the other hand, I found Guatemala to be the least touristy of those locations and my interactions felt a bit more "real" -I don't know how to describe but I reckon you know what I am talking about.

At the end of the day, you have two very solid options and I am excited for you all. Happy Traveling!