How sweet! and a good question.
After a difficult section better than before? Don't want to fall out on your first day of being engaged :lol:
Hhmm .. depends where you are starting I think, and if you want a 'religious' built sacred space or an inspiring 'natural' space.
If you start at St Jean then there is a point where you have crossed the hardest part and look out across Spain to wall after wall of lower mountains and you can see the long journey ahead of you. Symbolically this could be a good place, starting out on your life journey together ...
Or, there is the beautiful beautiful church - Eunate - before Puenta la Reina (day 4), which is not only a deeply sacred space but has the benefit of being off the main route so can be quite quiet ..
Or, you could complete the Camino without saying anything and then go on to Finisterre, stand at the world's end, looking out at the sun setting and ask that the next journey is with them, for life.
I met a Texan couple one year who had done the
Camino Frances together to see how they would get on in an extreme situation. They went home, got married, then came back for a honeymoon Camino - they were a delight.
Whatever you decide, have an open and vulnerable heart - and good luck.