Not to worry! With the ranked ballot, as long as you rank BOTH of the proportional representation options as your first AND second choices (in either order), you will be increasing the chances of a majority vote for one of the forms of Proportional Representation.
The way it works is: if no option is popular enough to pass the 50% mark to win the plebiscite, then Elections PEI will exclude whichever option was least-popular, and will 're-distribute' the votes. If you voted '1' for a choice that is excluded, then your number '2' vote will be counted instead, and added to all the other votes for that option!
Donald explains how this works in this video.