Honestly, do your drawing in autocad if that is the cad pckage you are most comfortable with (dassault draftsight is free (for personal use)) compatible software package), then open your dxf in sheetcam and generate your gcode there, after setting up your machine and defining a few tools (really simple).
Have a look on YouTube and search you,for sheetcam, there are a huge number of easy to follow detailed well presented tutorials.
Alternative 3d software (if you need 2.5d too) would be onshape, which is again free... But I must admit not sure about the export file format (one thing to watch... Don't draw something and then realise you can't do anything with it (like I did with emachineshop....))
Rob