4 + 1 more language?

First of all, I feel like I'm bad at getting to the point, so please bear with

So for context:

We are a little family of 3, I was born in Germany (German fluent) with Vietnamese heritage, can speak both languages and am speaking exclusively Vietnamese to our son (14months). My Vietnamese is okay, I'm conversational but missing many vocabulary, so I am taking lessons to improve.

Partner, Finnish, speaks Finnish to our son.

We both speak English to each other (partner can't speak German, understand a bit) but not directly to our son. Or not intentionally.

Community language is German, he is going to a German daycare.

We will move to Denmark next year and now we were wondering if we should put him to a international (English speaking) or Danish speaking daycare.

I was worried that 5 language is really a lot, we parents don't speak Danish at all and won't need to learn it for our jobs, although of course we will pick up a few words but far from fluent speaking level.

On top, I would like him to learn German as it's also a big part of my life and we might move back to Germany. So should I speak Vietnamese at home and outside of home German with him? Or how else could I maintain German exposure in Denmark?

We don't know how long we are staying there, it's open end. It could be that we just stay a few years 2,3 years or longer there.

Thanks for your advice :)