Phil, if you've had a lot of good air circulation around the boards they are probably down to 16 - 18% MC, which is higher than what you'd like to have for an indoor project.
If it were me, my first choice would be to stick them in an attic for a couple of weeks. This has two benefits - first it will bring the MC% down below 10% and second it will help to sterilize the wood. If you can't get them into your attic, do you have a friend or neighbor whose attic that they will fit into?
My second choice would be to put them into a humidity controlled environment, stacked and stickered with around 300 fpm of air blowing across and through the stacks. In a week, they should be below 10% if they are already below 20%. The drawback of this versus the attic is that you won't benefit from the heat sterilization.
From a MC% standpoint, you have the option to take exact dimensions of your boards, calculate the cubic inches, and weigh them. There are charts that list the weight of both green as well as 8%MC oak boards that you can use for comparison. Measuring them with a good high quality meter is your best option though.