The Sport is the kayak you want. Light, portable, great stability, and room to grow if you're a kid. In fact, the Sport was my first Hobie kayak and I was (still am) 5'7" 205lbs. I took it to inshore waters and offshore. It is quite capable for it's size.
Only two cons to the Sport:
1. Without the rudder, paddling the Sport reveals that it doesn't always like to go straight. This is simply the nature of all short kayaks
2. If you are an adult user in a sport, the weight capacity is only 225lbs, so pack light!
The Revo11 is also an excellent choice for a young kayaker or small adult. It is slimmer, sleeker, and longer than the Sport and can carry a bit more weight, but feels a bit more tippy if the user is more accustomed to wide kayaks like Outbacks. Standing in a Revo is also more tricky than in the Sport.
Good luck, you are an awesome parent for getting the kids involved