>Should we split the hive already if we find queen cells?
Yes. But you probably won't.
>Is it better to let them go naturally?
No. You'll lose half your bees.
>Have a second empty top bar waiting for bees, but wanted to make sure out first hive made it though the winter. Planning on inspecting the combs tomorrow if weather permits. Also, if we do split the hive, I'm concerned about genetic diversity as there are no bees around to mate with other than the drones in our hive.
That is your belief. It is a questionable one. There are often bees you don't know of.
> Do you think we are better of getting another swarm for the second hive?
Splitting is a normal part of beekeeping.http://www.bushfarms.com/beesswarmcontrol.htmhttp://www.bushfarms.com/beessplits.htm