Larger events can either mean more people or a longer time period. Either takes more work.
Larger events might include
Conferences (multi-day, multi-track)
Dates & times for larger events
Not-too-close to holidays
Stay away from school breaks when people are likely to be on vacation
Research other local events that is happening on the same month, so they are not to close together. You might have the same attendees.
Avoid Mondays because its often a business day with staff meetings and submittals. Thursday + Friday or Friday + Saturday are good days.
Create a event handout with schedules, map, times, and speakers
For long events, make sure there are breaks and ample snacks and coffee to keep people energized.
Partnerships and sponsorship are extra important for larger events
Creating a budget is essential (in Google Sheets or MS Excel). Budget items should include...
Venue/ room rental / parking
Marketing (flier, ads)
Event materials (name tags, printed materials & handouts)
Equipment rentals (AV, transportation)
Speakers and presenters? (If you pay speakers, you are likely to loose money unless you're able to charge a lot for the event. What are speakers' goals for the event?)
(Receptions/ side events?)
Price tickets based on the costs you've outlined in your budget.
Try to break-even, but also give yourself a little padding so you don't make money.
Create low/ medium/ and high projections for attendance.
If you make a bit of money, it can help finance group activities or help host the next event.
See if you can get the sessions approved for continuing education units
Have instructors create a class hand-out
Are instructors getting out of the event what they need? How are they being compensated (monetarily, or otherwise)?
There are many online resources on how to host hackatons (e.g. hackathon.guide)
Problem framing is important for getting to meaningful and useful outcomes.
Recruiting & team formation is a very important part of the process.
How can you get the right people there?
Can you form functional teams?
How can you help incorporate and embed diverse skillsets and perspectives?
Other considerations include: Prizes, Judges, preparation (perhaps including training), hosting and facilitating space and food, intellectual property
Conferences might be a multi-day event that includes both training and hack-a-thons.
Think about pre-events and post-events (parties, dinners, receptions)
Create an event program hand-out that shows the schedule and a map.
Sched is a good digital tool for events with more complex agendas and multiple speakers.
One way to have a bigger splash without organizing everything yourself is doing an event before, during, or after another large conference (like Autodesk University, the AIA conference, or regional gatherings). You can share an audience with that event, and might be able to use some of the same spaces and infrastructure.