Most park entrances are only open during daylight hours (6am to 6pm), so entering after hours might be considered a violation of park rules.
I didn't pay attention to signs along the roads when last there (too busy looking for wildlife while my driver did the navigation), so can't say how well signposted the routes are within the park. But that could be a huge factor when driving in the dark.
Best bet is to call or email the lodge office and ask them. They would know the park restrictions on nighttime driving or entry.
In terms of safety from animals or poachers... I would think that poachers would not use the main park roads to avoid running into park officials, so you wouldn't likely encounter any night time hunts (but you might need to explain why you are out there if you encounter a ranger patrol).
But there could be more wildlife on or near the road as they would be used to no traffic at night, so you would need to keep the eyes open.