How big is the room? Do you need a crib or could you just get a pack and play for the baby?

It would help to see the space, but I would maybe do a gray and white-ish horizontal stripped wall and do pink linens that way the pink can be easily changed if pink wears on you. Gray and white can go with anything. Good luck. The stripes in photo are not the same colors but just to give you an idea.

I'm totally confused -- is the baby there all the time, and the adults visit occasionally? Or would all three be visitors, in which case why consider it a nursery? Or... ??

For a duel purpose room, I like the idea of a wall bed. This is a living area , but you could get a general idea of what I mean. The bed would fold up neatly behind a cabinet when guests aren't using it to keep the area free for the baby to play.

The beds below are on Craigslist. The wallpaper is from Etsy. I would use it on an accent wall.

Wallpaper

Bed

Bed

Here are some inspiration photos...

I like the furniture arrangement in this room: