I like to think of kids dancing to have fun and not get in shape. If you want a kid, especially one who is just five years of age to really love dancing and engage with it lifelong, it is best to device ways of making dance fun. Resistance training (body weight, using bands or free weights) has been shown in athletics to really benefit children starting at the ages of 6-8 years. You will however need to exercise caution in the design of the program as their bodies are still developing. And figure out ways of making it engaging and fun!
To get a shining star to rise at that age is far less of a hurdle than keeping that star from sinking when she/he is older. Let them rise slowly but help them as teachers to shine longer and brighter! And yes, definitely include strength and conditioning – in measured doses, close monitoring and with loads of fun!