Amazing Idea: to be seen... with no information and just your word on it being amazing, I would guess "generic-genre-mashup-shooter-RPG-MMO-no.99999". But go ahead and prove me wrong, tell us more about it (as much as you feel comfortable telling at the current stage of the idea), I am pretty sure you will get very good input on your idea here no matter if its seen as good or bad idea by the majority.
Oh, and if you are afraid you idea might be stolen. Don't. Read the stickies in the game design subforums, one of them actually adresses just this fear shared by most newbies to game development.
EDIT: While trying to locate said Stickie I didn't find it anymore... The gist of it:
Nobody will steal your idea because:
1) Ideas are a dime in a dozen
2) most of them are not as good as its source thinks it is
3) even if the idea is good, most people on this forum either have their own ideas they want to implement
4) or chances are little that people without ideas of their own actually will steal the idea and implement it
5) and forget about someone selling the idea to a studio or something like that... not going to happen
6) yes, that includes you selling it
7) the execution is what counts, not the idea. Two games can implement the same idea but with vast differing execution, one of them will be a huge success, the other an utter failure?
Who would have thought a survival/building game with blocky retro graphics and no real story or gameplay elements besides building and figthing monsters would be a good idea? Yet the execution minecraft gave to that idea was good enough it found a huge audience even with its blocky graphics style.
Developers to do the work for me: Either you are rich or not gonna happen. Go ahead, try the classifieds... but be prepared to make a VERY GOOD pitch to every person that might be interested to work with you. With no prior expierience, no work done yet on the project, and no skills you can bring to the table, you will face an uphill struggle.
If you are interested in game development and have an awesome idea, aquire the skills to make this idea a reality. If you are interested in funding your awesome idea, aquire the money needed to hire professionals.
Do NOT try be cheap with time and money here, chances to find hobbysts that work on other peoples projects WITHOUT having an at least halffinished, very promising looking product yet, WITHOUT pay (future profit shares will not motivate most people) will be almost impossible.
Release on all Platforms: I hope you are aware while many modern engines are multiplatforms and allow you to build the game for many platforms with some simple klicks, there is still a lot of overhead to releasing on multiple platforms (aspect ratios and resolutions changes, optimization for different hardware (if you do not pick the lowest platform, you will have to cut down graphics and physics between mobile and PC for example), releasing and marketing to different markets and storefronts).
If you have limited resources and expierience, pick one platform and stick to that. You can always release it for a different platform later on.
Engine: Depends on your game concept a lot, without further information, any engine could be best. At least the big ones (Unity, Unreal Engine 4, CryEngine...) can be used for almost all game genres and 3D projects you can think of.
All of them have their strengths and weaknesses, maybe read them up before commiting. That said, you cannot go wrong with Unity or Unreal Engine, I have thorough expierience with Unity and just started with Unreal, both of them are good engines with big communites behind that. My expierience with CryEngine wasn't so positive, but then I gave up quickly as it didn't do anything better really than the others, while having a pretty buggy example project and dated looking editor.
Language: depends on the engine, and what your programmer knows (that is also why either you should let the programmer you can motivate to work with you decide the engine/technology, or you should decide on that and then specifically look for someone expierienced working with that engine/technology (harder to do as you now narrowed down possible candidates a lot)).
C# is the best choice for Unity, altough Unityscript (Javascript like syntax) or Boo is also possible.
C++ is the best choice for Unreal Engine, altough you do get a visual scripting interface in the form of Blueprint.
And so on....