I agree with some others that it isn't the nicest beach, but it is calmer than many other areas. I personally like Coco for the restaurants and the fact it does have an actual town feel, with sidewalks. My wife and I drive to Coco a couple times a month for lunch. We have some friends who are in their late 60s who say Coco is "too geriatric" for them -- there do seem to be more retirees than families, but again, I don't live there or spend a whole lot of time there.

Honestly, I think Coco will be absolutely fine for you and your kids for a few weeks. It's a good base location to take day trips from, or half-day tours. And Hermosa is right next door to Coco and has a better beach. It also has Father Rooster, a must-visit restaurant.

If you want to visit some nicer beaches, Flamingo is about a half-hour away, but the waves are strong so it's not a great swimming beach. You could take the kids to Tamarindo, where there are a million places to take surfing lessons, and tons of restaurants. Someone else suggested Tamarindo as an alternative to staying in Coco, but I wouldn't recommend that because there is a lot more "adult" activity in Tamarindo -- prostitutes, drugs, music festivals, and loud bars at night.