I'm all about the outside training personally
, and I think you'll be able to do it the way you have it planned. One thing I've noticed with my little boy Nikko is that it's more about the surface than it is a specific place (probably part of why indoor trained dogs can sometimes get confused between pee pads and rugs). Granted, Nikko has his favorite corner of the yard when it comes to pooping, but I think the main thing for him anyways was having gravel. We live in the desert, so our backyard is gravel not grass. I took him to a friend's house who has grass in their backyard, and gravel in their front... He didn't pee in their house, but he also wouldn't pee in the grass in the backyard either. Finally I took him to the front yard where there was gravel (even though it was a different sized gravel) and he peed right away for me.
So.... so long as both your pee/poo areas are under open sky and have a similar texture (be it grass or gravel or whatever), I don't think you'll be making it too much harder for your new boy. Of course it's probably best to have one place in the beginning to stick to for the majority of the time in the very beginning, but I wouldn't think it would cause too much of an issue honestly. Good luck... potty training is a TON of work, but sooooooo worth all the frustration and sacrifice of sanity it requires.
It's good you're putting some thought into it upfront - your new boy is going to appreciate it.
Lauren & Nikko