If you are staying at the Venetian, and get to Tao before midnight, there is no entry fee. Otherwise it is 20$. I won't be going back, but that is not because the place is not great, it is just a little loud for me. But, don't let that deter you. I should have worn ear plugs.
Tao Nightclub gets very crowded, so if you don't like crowds do not go there. The drinks are great but expensive. The service is very nice.
It is a nightclub and there is also a line to get in at night. The music is great, a lot of EDM. If you like to dance you will love it.
No kids in the nightclub. Enjoy.