Swan, yes, the Vatra is now primarily a cultural organization which celebrated it's 100th anniversary a few years ago. Its founding as a nationalist political organization preceded that of the modern Albanian republic in 1912 and was instrumental in securing international recognition of that independence. Most would also agree that Vatra's newspaper "Dielli" expresses a bias toward one of the current two major political parties in Albania and a distinct hostility toward the Archbishop of the Albanian Orthodox Church. You may find them at www.vatrafederation.org
The Muslim Albanians, both in Albania proper and the diaspora have rarely shown the reticence that Christian Albanians feel toward attending services or social events associated with the local Mosque or Teqe (Bektashi temple). Certainly, the fact that Muslim prayer is conducted in Arabic presents a major disincentive to attend prayer services. Whereas the Albanian Orthodox parishes use Albanian and English (in USA) with the possibility that Romanian, Greek, or Slavonic might be the dominant language of worship depending upon the ethno-linguistic make-up of the congregation. In Selenica, it's Romanian. In Saranda, it's Greek. In Liqenas, it's Slavonic. As it should be!
In Philadelphia at the Albanian Orthodox Church of Sts. Peter & Paul, one will normally hear during the Divine Liturgy, in order of plurality: English, Albanian, Slavonic/Russian, Romanian, and Greek. Up until our Georgian friends founded their own community a few years back, we used that language as well.
Also in Philadelphia, the parish of St. John Chrysostom uses English almost exclusively since the departure of the Albanian-speaking deacons and chanters. The choir does what it can.
In both communities, it is normal to find Albanian Muslims attending both the worship and social activities. At least three of my Godchildren were from Muslim backgrounds.
Feel free to send me a private message to find out if I'm acquainted with your Godfather personally.