Sounds like a lot of fun, good luck!
I've never attempted a lunch hour style game. But, I have run a weeknight game, online, nearly every week for about a year. These games usually featured about 2 maybe 3 hours of actual play per session.
In my experience:
1. Don't worry about if players miss sessions. If someone can't make it, their character drops to the background. If they show up the next day, their character returns. Don't waste time working out what happens to their character.
2. Online via Roll20 has the advantage of being able to save state. In a real person game, maybe use something like Gaming Paper that you can roll up and set up again. Alternately, if you have a presentation room, you can put your laptop with Roll20 up on the display and use it for your maps.
3. I recommend using an old-school concept of a Caller. Have the players designate a Caller for each session. This person informs the DM of the actions the party takes. This helps speed up discussion and communication.
4. Run something simple and easy to manage. I had the most success with a dungeon crawl. I originally ran my online game using Dyson's Delve. They went in, explored as much as they could, and then they left. When I tried to do more with the game (story lines, wilderness travel, etc) was when the game started losing focus. Whatever you choose to do, keep the focus tight.
5. In my experience, I had a problem with disparity between Short Rest recovery classes and Long Rest recovery classes. When we played online, we had time for 1 or 2 combats. I'd recommend using the option of Short Rest 1/day, Long Rest 1/week from the DMG. Otherwise Barbarians raging every combat and Wizards going nova tilts balance and effectiveness away from fighters or rogues a bit.
6. Use whatever techniques you can to speed up combat. Combat in 5E can really drag, since every character has so many things it can do. I recommend... 1. Use side initiative. 2. Roll attacks and damage together (or maybe just use average HP and damage). 3. Buy or make spell cards for casters. 4. Use the Cleave rule from the DMG to help against low level creatures.
I've never attempted a lunch hour style game. But, I have run a weeknight game, online, nearly every week for about a year. These games usually featured about 2 maybe 3 hours of actual play per session.
In my experience:
1. Don't worry about if players miss sessions. If someone can't make it, their character drops to the background. If they show up the next day, their character returns. Don't waste time working out what happens to their character.
2. Online via Roll20 has the advantage of being able to save state. In a real person game, maybe use something like Gaming Paper that you can roll up and set up again. Alternately, if you have a presentation room, you can put your laptop with Roll20 up on the display and use it for your maps.
3. I recommend using an old-school concept of a Caller. Have the players designate a Caller for each session. This person informs the DM of the actions the party takes. This helps speed up discussion and communication.
4. Run something simple and easy to manage. I had the most success with a dungeon crawl. I originally ran my online game using Dyson's Delve. They went in, explored as much as they could, and then they left. When I tried to do more with the game (story lines, wilderness travel, etc) was when the game started losing focus. Whatever you choose to do, keep the focus tight.
5. In my experience, I had a problem with disparity between Short Rest recovery classes and Long Rest recovery classes. When we played online, we had time for 1 or 2 combats. I'd recommend using the option of Short Rest 1/day, Long Rest 1/week from the DMG. Otherwise Barbarians raging every combat and Wizards going nova tilts balance and effectiveness away from fighters or rogues a bit.
6. Use whatever techniques you can to speed up combat. Combat in 5E can really drag, since every character has so many things it can do. I recommend... 1. Use side initiative. 2. Roll attacks and damage together (or maybe just use average HP and damage). 3. Buy or make spell cards for casters. 4. Use the Cleave rule from the DMG to help against low level creatures.