Provide some cover for your BG and they will flourish in no time at all.. Also you could cage raise the BG's fr the rest of the summer then they'll definately make it.. Don't waste your time with goldfish..
Another option to look into is sectioning off a pen of sorts.I know a forum member had a post where he used a corner of his pond sectioned off.So he could raise some fish out of reach from his lmb that seemed successful.
I would never pay 400$ for 100 BG,if it was me I'd be out when I had time with a fishing pole and a bobber filling a bucket or two,but that's me and again I have good hatcheries close at hand

There are many ways to skin a cat fish on here,maybe look into transporting them yourself?I think a bilge pump and a old cooler would be a lot less then what they want to charge you.Again quite a few posts on this setup and subject too.