Again, when does Duo want us to use "on est.." and "Nous sommes...?"
You can use both if you want. I am sure that both are accepted:
I just tried "On est vraiment enchantés de notre voyage", so it definitely works. I usually try the "On" version since when Duo gives us the French version, it's almost always the "Nous", so I'm learning that anyway.
"nous sommes beaucoup enchantes de notre voyage" why isn't beaucoup accepted here as a synonym for vraiment when it's suggested as a synonym in other sentences?