Anything below a 430 is just a toy really. 430 is a great head, with linked zoom, sensor crop detection, 2nd curtain, hss, flash modelling preview etc.
If you are willing to carry a 430EX is it really that much of a difference in carrying the gun you already have? The 600?
Why not expand rather than augment your kit? It's not like the 430EX is much use to you in a system with the 600 (i.e you can't do multi off camera flash mixing radio and E-TTL wireless)
I would take the 600, and spend the flashgun money on a video monopod (manfrotto 680B or similar) as the pivot foot will be great for panning shots with slow shutter as the family pass on the roller coaster. Or plug a gap in your lens range.
Just seems excessive.