Ya, 7 does not go easily into 2 to create a final. How about this:
Group 1: 4 entries, top 2 advance
Group 2: 3 entries, top 2 advance
Semi-final 1: winner of Group 1, 2nd place Group 2
Semi final 2: winner of Group 2, 2nd place Group 1
And then through usual final with the two winners