Be careful with that relay circuit... the contact resistance of a highish-current relay is not all that great. A popular example is the Song Chuan 832A series, which specifies "<50mΩ, @1A/6VDC, initial". This is... not great if you are very concerned about IR drop over the lifetime of the thing. I don't think they're actually that bad in practice, but the spec sure allows them to be. Alas, you won't (okay, I couldn't) do better with a different vendor; many are even worse at 100mΩ.
So if you are very bothered about such things, MOSFETs are often better.