Yep. It takes effort to get astringency from a batch sparge, so just use whatever is left over after mashing.
That's all I do, it typically ends up around half and half for mash in and sparge when I am sparging. Additionally I use hot tap water with a campden tablet and just sparge with that, works pretty good and saves a lot of time.
Thought I responded to this already, but guess not. That's plenty close IMO. You should be just fine.
