Grab a picnic, blanket or lawn chair and hear — or dance to — Vashon’s oldest garage band, The Portage Fill, play the final Concerts in the Park show from 7 to 9 p.m. Thursday at Ober Park. The band features two vocalists, full horn, sax and rhythm sections, and plays Big Band swing tunes from the 1930s and 40s along with some blues, Latin and even a few rock ‘n’ roll numbers.