I'll give you my 2 cents:
As far as best lake for big bass - Hard to say, I saw a photo of a 12.5 lb. bass caught in Brittany this spring, Brittany certainly has some big bass and is not too bad for average size fish either. Windsor is a good lake for big bass, but getting any over 8 lbs. is tough, there are decent numbers of 4 - 7lb. bass in Windsor. Avalon also has some big bass, my personal best, 9.5 lbs. (approximately) came from Avalon. Lake Ann also has some good bass in the 4 - 7 lb. range.
Numbers? You can catch a bunch of 10-12 inch bass on Avalon. Windsor and Ann are good for numbers and better average size. I have not fished Loch Lomond much in the last few years, but it has decent numbers of bass also.
Crappie? Crappie fishing is tough in the BV lakes, lots of pressure. If you can go out and catch 6 keeper crappie in a day, you're doing darn good. If I had to choose a lake for crappie, I'd probably go to Avalon, lots of brush piles and they stocked several thousand fingerlings in there a couple of years ago and they should be around keepers sized by now.
The lakes are fairly murky right now from the rains we received this spring, but unless there's a gully washer before you get here, they should be in great shape by the end of May.
When you get close to coming down here, feel free to shoot me a PM and I'll tell you what's going on.
Another option for your wife, if she likes panfish, is there are some good bluegills (8-10") in Lakes Ann, Windsor, and Loch Lomond. I like to use a #8 Eagle Claw longshank panfish hook, and a split shot (no bobber), use a redworm hooked one tijme through the middle, or a cricket and fish flats 6 -10 feet deep.