Understanding source and return current flow on PCBs
The best advice I can give is to use a 4L board, so you can have a solid ground plane. That in itself will make things a lot easier, as you will have the return current running pretty much right under the trace carrying the forward current. 

The cost difference is really not that big if what you are doing matters to you and is not crazy high volume (10.000+). You may save board space and routing time as well, which helps offset the small added cost.