A good cause isn't enough
Cutting corners is not a good idea. Even if it helps raise money for the cause.
A charity event site recently gave tips about how to cut corners on t-shirts, which are usually the largest single item in a race budget, so more money would be available for the cause.
That was not appropriate advice.
If you held a banquet fund-raiser, would you skip the main course because it cost too much? If you held a theater benefit, would you make people stand because chairs were too expensive?
If you want people to participate in an event, telling them, "it's for a good cause" isn't enough. They have to benefit from participation, too. (That's why so many events try to be "fun").
If you can't raise enough money with a race, then don't produce a race. Do something else, instead.