How to add tolerances/gaps in 123d Design?
Unfortunately, 123D Design doesn't have such a feature.

You could select multiple surfaces and push/pull them all at the same time though.

Remember, your 3D Printer's slicer should have an option to undersize or oversize holes and walls, to help reduce/remove the effect you talk about. 
It's called size correction, I think? Simplify3D Has it, atleast. 
You might have to tweak this for every filament type, though.