IMO the ability to withhold free will/choice is a false assumption in anything biologogical. How would it be restricted? Would you have to create a species of followers and a species of leaders? If so, what would decide the path a leader would follow without free will?

...if I am walking down the road and see someones' house on fire should I interfere?...where does "responsibility" come in, if at all?...

I would not give them free will because if you give anything free will you will then be ultimately responsible for every thing that this species does, good AND bad. This is the same thing as when believers say God is not responsible for what humanity does to each other because he gave them free will which is bullshit

If I helped develop them haven't I already interfered? And if I have already interfered, wouldn't I logically continue to do so?

I'd undermine the effort to increase another species's sentience and intelligence. I don't think we have the right to impose that; there's no opportunity to consent to such manipulation. If unsuccessful in that endeavor, I'd avoid meddling in the development of the species — with the possible exception of providing medical service to correct any serious problems that were a direct result of our initial interference.

Free will... man has kept down the population of earth though wars. Natural disasters have help with the popularion explosion. Diseases have wiped out civilizations and has kept the population down. Where did these diseases come from? What natural disaster is going to happen to thin humans out? Whats going to cause it. The earth is due a natural disaster. If it doesn't happen soon the earth will over populate within the next 150 years. The sea may rise 5 feet by then and slow the population explosion down. I think we're in for some terrible times. I sure am glad my life span is almost over. I figure i got ten to fifteen years left. I feel bad for the children thats going to have to fix things around here.

I suppose since we are dealing with earth we would not be bound by the limits of the Prime Directive. If possible, I would be inclined to put something in the DNA that would encourage a more logical, rather than superstitious, species to evolve. I wouldn't want them to be full on Vulcan, where they have to suppress all emotions because they are so intense; and I would not want them to be without any emotions. Some Vulcan logic along with some healthy, controllable, emotions would be good.