Frame rate

Hi, I'm an audio technician and lately i started to make some simple videos for musicians, so I encounter some difficulties dued to lacks of knowledge.
In my last videos i noticed that recording at 25 fps I had problems syncing audio, because we use more points for a second of time and not only 25, so I decided to increase fps to 50 while recording. I used 5 camcorders, 3 of them at 50fps and 2 at 25fps and I created a timeline at 50fps.
I thought that at the end of the project I could have downgrade the export file at 25 fps, but my only choice is 50.
I imagine that my audio way of thinking is wrong for video, so I have two questions:
1) Can I export at 25?
2) Which is the best way to manage this kind of job next time?

2) Which is the best way to manage this kind of job next time?

Film production, like audio production, requires education and experience to do well.

If you don't have that training or experience, hire someone who does.

I mean, you don't want the camera guy mixing the song, do ya?

Just use 25p as start. 50p files will have every 2nd frame dropped. Next time if you need 25p then set all cameras to 25p