Bees travel from flower to flower and which does mean they will transfer pollen from different varieties of watermelon.
Watermelons do not cross pollinate with many other plants, but different varieties of watermelons will however cross pollinate.
You can plant them together, but be prepared to have possible mixed between the vines.
I do want to add that cross pollination (via bees) between the two varieties melons may affect the quality (shape and sweetness) of the melons that come out, but I've never had a problem.
Planting more than one variety of watermelon close to each other should not be a problem at all. Just make sure that you space the plants according to the seed pack directions. Watermelons need LOT of space systematic bud pinching to grow nice-sized ones. If you're worried about any other plants growing near your watermelons (which is rarely a problem), you can look at this article: What Plants Should Not Be Planted Next to Watermelons? http://homeguides.sfgate.com/plants-should-not-planted-next-watermelons-56374.html