It would be best if they were separate. The female will probably end up fighting and the male may over breed her. Some people do keep colonies with large groups of rabbits all together, but you'll be able to control everything better and know when to expect babies if they're separate.
Remember that when breeding, always bring to female to the male. Otherwise she will be territorial and could seriously injure the male.
I would build two large tractors for them. Be sure to predator proof with hardware cloth just like you would with chickens. When on dirt, rabbits will try to dig out so keep that in mind when designing the tractor.
There should be protection from the weather as well. Rabbits are prone to heat stroke, so plenty of shade and a big water dish is important.