If the Ottomans manage to take Ionia, you can claim both Crete and the vassalization of Venice itself. Vassalization needs 70%, if Crete is worth something like 16% etc. you may be lucky in the peace res. and be able to take both, (Crete and vas.).
If the OE withdraws from the war, leaving Ionia, you'll have to get Iona to get 100%, then you're only able to claim the two provinces, probably ca. (16+10)%, 26%... and you'll have to vassallize Venice in another war.
You wrote that Cyprus is a Venetian vassal, that isn't any problem. Venice can't annex it 'cause it's an island, but through a certain event (Catarina something) Venice will take it someday. While Venice can't diploannex Cyprus, doesn't mean that you can't either war-annex or war-vassalize Venice... just go on, do it.
And just a tip conserning Venice... If you mean to take down the whole nation (from the start), try not to take all its land possessions in the first war(s). You'll need to occupy most of the nation, but occupying the islands are often difficult. It would be better for you to claim the island(s) in the first war(s) rather than taking Venice's landpossessions, 'cause in the next war you won't have to occupy all the islands once again. The remaining continental areas could be taken later...
This strategy works even better if you have cores on Venetian islands and territory. (OE, BYZ, ATH, KAR, TRE). As the OE you can just occupy the continent, probably Dalmatia, Istria, Venezia, possibly Mantua and Ragusa.... with all these territories you should have ca. 50%, then you can claim all those unreacheble islands, like Crete, Corfu, Ionia and Cyprus... pretty simple, in the next war(s) take the remaining islands and the mainland, and in the end a Venezia with a cot...
