We love the buffet at Rio for dinner. It's a bit off the strip but there's a free shuttle from Harrahs. They have the best selection. A tepanaki (sp?) station, seafood selections every night, soup, salad, carving station, chinese food station, mexican station and italian station. They also have a lot of kid friendly food (corn dogs, mac & cheese, pizza, mashed potatoes, fries). It's not cheap but it's really good.
And in our opinion the Flamingo has the best breakfast buffet. They have tons of fresh fruit, a made to order omelet station, fresh made crepe station and then all the usual breakfast foods. Plus you can sit by the window and watch the flamingos and fish while you eat.
If you're looking for cheap buffets, your best bet is going to be downtown. I've never eaten at any of them, but I know they are much more reasonable priced than the strip buffets.
If you're looking for good italian, in Caesars Palace there is a restarant called Trevi. It is really good. The down side is they don't have a kids menu, but they will split a plate for kids.
For good mexican, there's a restaraunt in NY NY. I can't recall the name but it's the only mexican in there. It's pretty good and very reasonably priced for being the strip.
If you have picky kids and you're looking for something familiar that you know they like there's tons of chain restaraunts on the strip. There's Outback, Hardrock, PF Changs, Cheesecake factory, Rainforest Cafe. And there's also McDonalds, Chipotle and Panda Express.
I would also check out Serendipity at Caesars Palace. They have regular food that should please a picky eater(soups, sandwiches, nachos) but they're ice cream deserts are too die for. They are huge, you only need one for every 2-3 people but that's what they're known for. Yum Yum Yum!!!
If you have any questions or need any help with planning or anything, let me know. I live in Vegas so I'm pretty familiar with most things