I would not use a gopro for a christening ok for action stuff where your worried about damaging your cam ,the gopro is limiting no tilt out screen ,no zoom ,not good in low light
sound will be poor ,ok the black has 4k which is usefull but the lenses distort images so you will have to correct in post .although it can be done well if your name is phillip bloom
I would go for panasonic ,canon or sony hd cam where you will have all the features and image stabilization with better optics etc a dedicated hd cam will make life easier over a action cam