I reckon the ideal is 3 actual cams plus a GoPro if there is somewhere suitable to place it (placing a GoPro is by no means easy at every wedding even though you'd think it would be).
This ensures that you can cover the bride plus the groom plus have a wide angle / scene setter, and cut to the GoPro for extra effect. You should be able to operate one of the 3 main cams at any time to accomplish appropriate reframing / change to vicar / change to readers / change to guest shots etc. Meanwhile the other two cams are locked down either temporarily or permanently depending on the venue regulations regarding movement and the practicality of you moving positions without causing distractions or ruining the stills compositions.
However in practice churches seldom meet ideal shooting conditions even with the most cooperative of celebrants because of their physical features and layouts.
For example this forward area has no suitable position from which to capture the brides face and no chance of shooting from within or oblique to the altar area (were that even desirable):
Ashton Lamont Custom 404
In these conditions the small cams that work well in low light such as the ridiculously cheap Panny X900 can be a godsend as can place or clamp them anywhere. Look on the stone shelf above the left fellows head in this photo to see one in action:
Ashton Lamont Custom 404
I also had a GoPro on a lightstand just off centre right above the guest in the white tie.
A second cam was placed right at the back of the church for this view:
Ashton Lamont Custom 404
The third cam was positioned at the front in line with but several yards away from the left of the assembly in front of the altar (see 1st photo of altar area) from which I could shoot the grooms face – if indeed he ever looked sideways rather than forwards, and also get the readers and cutaways to the guests:
Ashton Lamont Custom 404
Ashton Lamont Custom 404
These are stills rather than frame grabs but you get the idea.
Its a case in point where even with a very co-operative celebrant and an enthusiastic couple you can only do what you can do.
I would be very reluctant to mount locked off cams on substantial tripods as they soon wreck the ambience of the event, going some way to being why wedding videography s not nearly as popular as it ought to be. Try using single column lightstands with heads instead – the new small cams usually have very effective IS built in so a little vibration is a non-issue. Or use magic arms and clamps.
At this wedding it was completely impossible to shoot from ahead of the couple (this shot with a Canon 15mm fisheye:
http://www.ashtonlamont.co.uk/641-mpgs/images/028.jpg
I had a GoPro on a lightstand immediately left of the camera position, a clamped cam on the rails behind the vicar, a locked off cam on a lightstand at the rear, and the main cam with me for this:
http://www.ashtonlamont.co.uk/641-mpgs/images/058.jpg
http://www.ashtonlamont.co.uk/641-mpgs/images/042.jpg
A civil ceremony showing two cams at the front. Its not obvious but there is a string quartet front left so no room for anything there other than a lightstand with a small cam on it behind their seats. Main cam on this occasion is front right. 3rd cam was locked off at the rear after the processional:
http://www.ashtonlamont.co.uk/636-gmrs/images/030.jpg
http://www.ashtonlamont.co.uk/636-gmrs/images/037.jpg
I shoot alone. Imagine what its like if a photog and a videog are fighting for positions front right! Horrendous for the ambience.
One last one. Again impossible to get ahead of the couple or shoot through the railings:
http://www.ashtonlamont.co.uk/631-gjpl/images/049.jpg
But a small black cam you can just see clamped to the wooden structure top right captured the couples faces, ring exchange etc beautifully:
http://www.ashtonlamont.co.uk/631-gjpl/images/054.jpg
Its always worth it to get along to the rehearsal if its an unfamiliar venue or if you think you may not have much prep time on the day. You can then think it through and try stuff out without feeling any pressure.
Pete