At the end of the day, the most important thing is getting the cardio session in. Worrying about doing it in the AM or PM is nit picking.
I train people for bodybuilding shows for a living. When my clients have jobs that require them to start very early, I will have them do their cardio after dinner instead of before breakfast. There is NO difference in results VS clients who do their cardio before breakfast.
Just get the cardio session in. That's what matters the most.
To prevent the cardio negatively effecting your sleep, stick with long duration low intensity steady state cardio. You won't want to do anything too taxing before bed because it'll rev up your central nervous system and might cause troubles sleeping.