I'm not sure what I'd do. Are there a lot of niche surfing sites out there? Persaonlly I would think the surfing niche might be more fun to build and research. Probably not a ton of competition either (just guessing).
If you went with the mom's making money online, you'd be going up against a zillion others in the same niche. Lot's of competition, hard to stand out.
Either way you'd have to decide what route fits your goals best.
Just my two cents. Good luck.
Jason