Advice on Coplanar Waveguide and Ground layout of Antenna
I have been using these general guidelines in transmission line design:  


To have a continuous GND connection between planes on different layers, the distance between GND vias should be below 0.1 wavelength.
You should calculate your wavelength carefully as it depends on the dielectric you are using.  
Vias have parasitic inductance; multiple vias reduce parasitic inductance and create lower impedance path between GND planes on separate layers.  
The GND planes on both sides of the co-planar waveguide should extend to at least 5x width of the line.  
I like to use co-planar wave-guides because it is easy to add components along the line where needed. So, basically it is OK to place components on the line as long as you consider the size of the pads of the components- ideally they should be the same width as the line width. So 0201 components will require thinner line than 0402, for example.
Additionally, when placing components between the line and the near GND, you would like to reduce parasitics, so I usually place 2 GND vias near each component I place.  
It is also important to keep everything as symmetric as possible. So an ideal placement of a component will be to both sides of the line. So, for example, if I would like to place a 1pF to GND, I would place two 0.5pF in opposite directions on the line.
Having said that, for 2.4GHz I usually don't follow the last guidelines and so far had no issues with that.