First, Welcome to the forum. Second, your question is usually the opposite of what people ask here. That being said, If you only want 2 hives you can just let them be bees and let them swarm when they see fit. If you don't want them to swarm and you have the flexibility of having one or two more hives during the summer, you could do splits then recombine them in the fall. Also, you could sell or give away your splits. If you join a bee club or place an ad on craigslist, I'm sure you could find a home for any excess bees that you might have.
As far as destroying swarm cells, I don't know that there would be any good that would come from doing that. Usually that does more harm than good. Unfortunately, even with the most attentive beekeeper there is no way to completely prevent swarming. It's natural for the bees to reproduce(swarm) so if I only wanted a couple of hives, I would do some splits occasionally to help prevent them from swarming and sell them to help offset the original cost of the bees and equipment.
Hope this helps a little.