Pretty new myself, but some thoughts...
Might be a good idea to check out the auctions in your area and see which goats sell for what; if you're just planning to raise them up from kids then sell them once they mature, not breeding, then size really wouldn't matter since you wouldn't be in close contact with a bunch of meat wethers headed off the the sale barn, KWIM?
But too, dairy wethers can be had very cheaply, and I'm sure if you wanted to buy a quantity of them from someone, you could get a really good deal.
You could always have a mixed herd of the larger ones to get the job done quicker/be easier to sell for meat, and a few minis for milk... you would have to make sure any large breed males were wethered, though, to avoid disastrous pregnancies.
One thing to consider is your fencing... won't do you a bit of good to buy a herd only to have them slip out and become coyote fodder. Electric fencing over woven wire is your friend.

Also, since you're just moving in, I'd ask around to see what kind of problems other people in your area (that have animals) have with predators, and take appropriate steps to protect your herd. Are there alot of dogs running loose in the area?
I have two Nigie doelings, and just love them. Such sweet girls, and pretty too... and just the right size for me. Those big ol' gals weren't the way I wanted to start.
Well, anywho, congratulations on your new property; hope it goes well!