Background
Currently I'm half a year in my first job after finishing my engineering degree. I was hired as a software developer, but since my team presumably thinks I'm a horrible coder, I got promoted away to a project lead kind of position. So I most of my working hours writing mails, arranging meetings and skype conferences with third parties or drafting concepts and white papers. Maybe a fifth of my time spent in office is actually spent on producing actual code. I am fine with this role and think I'm doing reasonably well and feel appreciated, it's just not a role I initially expected nor have any prior experience with.
Situation
My company wants to sell their trademark algorithm in a new market sub-segment that requires utilization of a technology with which none of us has any experience yet. So the task fell on me to get familiar with this technology, find out what competitors are available, how we could integrate this technology in our existing framework etc.
It soon became obvious that, considering we want to be able to deliver a finished product with a very short deadline, we would need assistance in form of external development done by experts in that field if we want to release on time.
So I contacted several companies all over the world specialized in the field of that technology and asked whether they want to develop a component that our framework incorporates. We received valuable input and drafted requirements with the help of three different companies. Finally, all these companies made us an offer and we have a good foundation on which we can decide who gets acceptance of the bid. I told none of them that they're the only company we contacted with our inquiry We have three offers on our table, but obviously will only accept one of them. It'll be my job to then tell the other two that we'll have to decline. I maintained a very friendly and nice professional relationship with them.
Question
What is a professional way to decline the offers of those that were not awarded the contract?
I'd like them to know that I value the personal contact with them and their time spent on drafting offers and technical concepts and that we don't want to rule out that we might want to do business with them in the future regardless.
Also, some of those companies are very interesting. I might want to consider sending them my resume some day in the future, so I'd like them to keep me in good memory.
Bonus Question
Should I have told them they're not the only bidders in the field?