I would agree that doing something fun and raising money at the same time is a great combination. Especially for a worthy charity. It will be a huge undertaking though.
I can shed some light (pun intended) on charity walks and other similar events based on my own experience. Creating and organizing these events is a big part of what I do on a day-to-day basis. It takes a collaborative effort from a team of dedicated people to make these events happen. Depending on where you plan to hold the event, permission and permitting is a HUGE obstacle to overcome. Especially when fundraising is involved. You'll have to have a 501c3 charitable organization apply for an event permit with the cities involved and you'll have to get approval from local law enforcement for everything from safety to first aid to impact on traffic to access for handicapped. These all cost money. You may even have to get a business license to do it.
Then you have to put a substantial amount of promotion into these events to get any meaningful attendance. Facebook and forums alone won't do it. It takes grass routes and commercial advertising working together. The radio station I work for reaches just under a million listeners in Southern California and we advertise our events 8-10 times a day for 6 weeks. It also takes a website with fundraising capabilities, and it requires a unique idea that no one else is doing.
Simply Googling "Light The Night" will tell you that this idea is not original and the title is probably trademarked. We'd be in for a ton of competition from other events, and people will likely pick the more established ones. If you have a strong charity on board it will help, but usually the charities good at fundraising do these events themselves. We'd have to get creative and make it something nobody has ever experienced before.
I'm not trying to talk anyone out of organizing something like this. I'm just trying to share some things we need to think about before we dive headfirst into a failure. We need a solid idea with one good charity and we should look to plan AT LEAST six months out to properly execute it.
I see all of the glow runs, color runs, mud runs, zombie runs, 5k and 10k charity runs come up every year on my schedule, and only the truly great ones are successful. For a little perspective, the last charity mud run event I produced for CBS Radio made $150,000 in revenue, but it cost us $50,000 to put it on. At the end of the day we had 2,100 participants, which is hardly a large number when it comes to these types of things.
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first time to the states woo! 
