You can still be "ladylike" because you ARE wearing underwear, afterall. If things progress to the point where you become, moist, all you have to do is part your legs and voila! Fast access!
Now, will he think it odd that you keep taking selfies during the date? Don't know. If he notices or says anything, hand him the camera! I sure know what I'd do!
Be sure to let us know how it goes!