Depends on how stable you want the UAV to be. If the air is still, probably position/velocity/acceleration added with friction and drag would be a pretty accurate model and is not too difficult.
However, air is not still, and no matter what model you make, you can't predict wind. Neither it's strength nor direction. The effect of wind especially makes the calculation of drag difficult as it depends on the aerodynamicity of the UAV in the direction of the wind.
That said, unless someone here has created before a similar UAV to the one you are building, and used it in the same application as yours, I don't think you can get a clear answer. Best way would be to try it.
My suggestion is to try building a model that doesn't ignore the basics (e.g. basic fluid dynamics), but don't go out of your way either. If it turns out that it's not good enough, then ask for help on the particular behavior.