Before I founded my company, I worked for another startup that wasn’t very transparent. It was not a healthy/empowering environment.
Now, when dealing with things like partnerships, customers, and finance (runway, burn, revenue, fundraising, etc) I ask myself “what type of company would I want to work at?” and I always lean towards transparency.
Having said that, this needs to be done carefully. Instead of pumping everyone up about a potential partnership that could fall flat, you should try to be realistic and objective about it. “I’m really excited about a potential partnership with X. Even though this partnership will require we invest some resources doing Y, I see the possible benefits to the company as Z. From my perspective, this is a good opportunity for us. This isn’t finalized so I’ll keep you up to date on our progress. Let me know if you have any concerns or questions about this.”