A business ideal with a good cause!

Either niche or a general marketplace depends on many factors:
1. how much money you have or can raise.
2. the management team's capabilities & networks
3. the outcome of the product-market fitness test
4. the level of operating challenges in handling the old items
5. Make a choice between going straight to build a business or split some resources to keep the company survive while slow down the building of the business.
6. The business environment that worth to consider

The points above not exhaustive, but relatively important to help you to answer your question.