If all you are going to run on your track are 0-4-0 small steam or diesel engines and small two-axle rolling stock (typical narrow gauge short line equipment), then the slightly wobbly track may not be an issue at all (in some cases it may resemble the prototype more realistically!). You will have to try out your loco to see. Couple a few cars to it and try that also. Run it in both directions.
I have set up five different larger temporary layouts in the backyard on the grass and they have been quite wobbly at times. I have not had any issues with my LGB equipment, including all the Stainz locos, the F-7 ABA units, the 2-6-0 Mogul, and the Crocodile. I have not run my Aristo RDC on such track yet so I'll take the word of those who have. My Aristo GP-40 and RS-3 both ran fine on wobbly track as well as did my Bachman Heisler and Climax units. The Bachmann 2-8-0 Constellation did not like wobbly track and would derail continuously.
Having said all that, I would never install a permanent railroad with track that wobbly so I agree with all the advice previously offered in this thread.
Al