First of all talk to the priest or officiant about do's and dont's and your ranges of movement. If you are allowed to move freely during the ceremony, I would suggest you to choose pos. #1 to film exchange of vows and rings. Pos. 2 and 3 as you can see have better angle to cover the bride's side because she is apparently more important part of your video.Use pos. 2 or 3 if you have no chance to set your camera in the central isle for whatever reason (priest's objection, terrible back light, etc.) Talk to the marrying couple straight (!) and ask them who would they prefer to see better if you put into position of making a choice between the two.

Second, decide if you have to shoot non-stop (continuously) or stop and go (preferably). In the latter you can discreetly move around the chamber and get different angles and close ups of the families on BOTH!!! sides.
And last but not least, read my book Shoot-It-Yourself Wedding Video Guide.