Day trips to Loire valley

There are plenty that do trips, and they fall in a couple of categories. Some are companies that do trips starting in Paris where you take a bus (or if you're feeling rich, a car) from Paris, and others where you catch a train to the Loire Valley and get a tour from there. Catching the train means you spend less time on the road - the train takes an hour from Paris whereas going by road can take between 2hours and 2h30.

Prices vary, depending on what you want to do - a cookie cutter tour in a minibus that just drops you at the chateau gates and gives you 60 minutes on your own at each site can cost as little as 120€ per person per day. Bespoke tours with driver and guide start at about 900euros a day for two people

I think Simon pretty well described the range of tour options. There are many.

The Loire Valley is very spread out. For obvious reasons, each chateau is some distance from all of the others. Are there certain chateaux you particularly want to see, or do you just want a taste of a couple of them? The easiest ones to access from Paris are in the northeastern part of the Loire region.

We don't need a private tour. A bus tour would be okay. Ideally we want to see Chenonceau and Chambord.