Dine with Shamu yes or no

Is it better than the Orlando Sea World?

Behind the scenes yes or no

How long to do Sea World taking in everything.

Is there a water park there, do we bring bathing suits?

Is the food expensive, should we take snaks of our own and drinks??

Thank you for your time.

On the dine with shamu, I'd say it depends how old your kids are. We went a year ago with a 2 and 5 year old and while they thought it was neat, and loved the chocolate-covered Shamu cookies, they were restless for much of the time. As were other youngsters. If you're really into marine biology and are studying these things in school, it could be very interesting and helpful. You get to ask questions.
There is no waterpark there.
The shows, of course, are good.

Dine with Shamu - No.
imho, it'd be like:
"Dine With Inmates In San Quentin - See How They Live And Play And What They Eat!!!"
"Educational And Entertaining!!!"
"Fun For All Ages!!!"

I live in San Diego and go to SeaWorld frequently. We have had the breakfast with Shamu with our 2 yr old and it was a lot of fun. The food was pretty good and the trainers talk a lot about the whales.
I haven't done any of the tours, however if they mention "you get to touch a shark" and that is your draw, ask how big the shark is. I did go behind the scenes during a birthday party and the shark we saw was about 8 inches long. So, beware.
It is hard for me to say how long because we don't try to do everything in 1 day. But, I guess at least 1 full day. In the off season (right now) they are only open from 10am - 5pm. It would depend how many shows you want to see. If you went to 3 shows I think it would be pushing it, to get to everything else.
There isn't a waterpark, but there is a water area, in the summer, with water jets and fountains, I'm not sure what all is in there because my son has been too little. There is also the Shipwreck Rapids ride, like a rafting ride "you will get wet on", though I've not been on, son too little.
YES! The food is expensive, best of luck!
Have a great vacation!

you will need one full day and if it is during "off-season" then you may miss a few things. if you are going when it is open during the evening too, i'd recommend going out for lunch. mission beach is just a 5 minute drive away and you can get more reasonable meals around there. plus if it is hot, you could go walk in the ocean. then go back for the balance of the day.
the rapids ride is fun but you will get wet so if it is a cloudy, cool day, you may want to do this at the end of the day so you don't get too cold.
i recommend catching the first morning show for shamu. then you have the opportunity to see it again later in the day.
have fun, i love it there.