You might consider getting them a lunch or dinner on the Tour Eiffel. You need to make the reservations a long time ahead.

http://www.eiffel-tower.com/exploring-the-eiffel-tower/the-restaurants.html

Here are some fun ideas:

www.lindamathieu.com/paris/theme/index.shtml
www.paristalks.com/talks-walks/talks-walks.html

I would look at private tours and find something that is in line with their interests.

I've also done photo tours and they are very fun if one of them is into photography?

Depends on their interests, but a half or full day here would be my idea of heaven:

http://www.caudalie-usa.com/our-rates-Les-Etangs-de-Corot

Loire Valley Chateau Tour would be amazing.

Might look at a Stay at Chateau D'Esclimont

built in the 1400s by Archbishop of Tours

Booked mine on www.venere.com truly amazing experience

Fine dinig in the Chateau was incredible.

Do you know nothing about your in-laws' specific interests? Are they foodies? Are they interested in culture? Do they like dazzling spectacles? Is nature their thing?

It would be foolish for any of us to give suggestions without knowing anything, unless you are one of those people who just thinks that the amount of money spent is all that matters.

Wow Mr. K, the poster made it pretty clear what she was looking for...meal, guide, show, etc.

And if she hadn't mentioned a dollar range, would you have said
"It would be foolish for any of us to give suggestions without knowing your price point..."

Eiffel Tower restaurant woould be one.

On a similar theme:

http://www.cieldeparis.com/

Ciel is re-opening in April. Les Ombres (on same page) is another one. And another:

http://www.restaurant-cafedelhomme.com/

Also re-opening in 2012.

Apart from fact that two of these are being re-done, all have been recommended here in the past.

Something else:

http://www.4roues-sous-1parapluie.com/EN/index.html

My husband and I recently returned from Paris (we're your in-laws' ages) We had dinner at L'Atelier de Joel, at the counter, and it was a head-exploding kind of experience. Last time we went we had lunch at Lasserre, unbelievable. Both are in your price range. Check the website for Theatre de Champs-elysees if they like classical music - going to concerts there is really something special...and spring for a drink at the Plaza Athenee before they go to the concert! Their bar is to die from.
Buy them copies of "Avenue Montaigne" and "Paris, Je T'aime" to watch before they go. That will definitey get them in the mood!

Another nice place to eat:

www.chezfrancis-restaurant.com

Offer them dinner at Lasserre; at night the roll-back roof is opened (rainy night excepted) and the stars look down on the diners. Food presentation is incredible--I still remember the swan carved out of a block of ice that accompanied our desserts.

Wow -- these are wonderful ideas. I'm checking out the restaurants in more detail tonight. I love the idea of a guide, but these meals might be more memorable. Maybe I'll give them a book with some good self-guided walking tours instead ; )

And thank you, Kerouac, for asking for more detail. My in-laws aren't foodies, but they enjoy nice food. They're not art buffs, but they like learning about new things. Money is definitely not the important part of the gift, but we want to help them experience something in Paris that they might not do on their own.

Thanks again everyone for the ideas. I think they'll love it.

Take a look at Cookin With Class. They have half day and full day classes and are within your price range. We did the half day macaron class and absolutely loved it!

One day in May a couple of years ago I had lunch at Le Cinq and in the evening went to a ballet at the Palais Garnier. Performance was Roland Petit's Proust ou les Intermittences du Coeur, based on Proust's Recherche du Temps Perdu. This day epitomized my Paris fantasy (have loved Proust since college and I still sometimes see Paris through the prism of his work). But that's just me!

That same trip, I hired a dining consultant, "Julot," whom I had met on chowhound. I highly recommend him *if* they are in any way food people. http://www.zeparisian.com

You are a very thoughtful son/daughter.

One of the most popular formulas for visitors from other parts of France or Europe are the combined Flo Brasserie meals with theatre tickets. Of course, it is easier for people to find a spectacle they want to see if they speak French...

http://www.flobrasseries.com/spectacles/en/

A meal and/or show is fairly standard. Look at GraceJoan's thread, she does it everyday.

For a memorable experience, I would arrange cooking classes (in the Ritz kitchens perhaps,) or a garden visit with private driver, to Monet's garden at Giverny for instance. That would be fabulous in May.

Take a look at what Lisa Buros has to offer. She runs "your Paris experience" and you may find something there (or she may be able to suggest things).

http://yourparisexperience.com/

If I were the lucky recipient I'd like a dinner at the Tour d'Argent, at a window table if possible.

Do your parents like wine? Want to learn more about it? For my birthday a few years ago we had a wine tasting with O Chateau. Olivier is great fun and we learned a lot that was helpful in choosing wine in France and elsewhere even after the tasting. That would be a good introduction for your parents for the rest of the trip and something to share with the other family members too. http://www.o-chateau.com/paris-wine-tasting. When we did it Olivier was still hosting tastings in his loft apartment but now he has a full wine bar and offers quite a range of options. They also now have some combinations of tastings and cruise on Seine. (See "Paris Packages" on that same wine tasting page.)

Hi GG,

Let them live like the rich and famous for lunch: at www.taillevent.com 80E pp + wine.

If they like art, a guided tour of the Musee d'Orsay or Louvre would make a great gift.

If they like a raucous wine tasting, Chateau O is fun.

Thank you everyone for the great ideas. It was a hard decision, but we ended up booking
http://www.4roues-sous-1parapluie.com/EN/index.html. It sounds really fun and just right for them. (On my next trip, though, I'm going to some of these amazing restaurants.)

Thanks again!

greengiant----I'm curious,which tour did you choose? I checked out the sight and they have some interesting things to choose from.

Michel_Paris what a good recommendation.

An expedition to Giverny in a private car, with plenty of time for Monet's house and garden, a nice lunch and the American impressionist museum would make this parent happy if our children were in a position to afford it.

Have they been to Paris before? Or even if not, a day tour with Michael Osman --maybe highlight the two major museums, and a couple of other places in the city, and then a nice dinner at night. Michael (once you reach him) could make the reservations for you. He would not be at dinner! He is a superb guide--he will tailor it entirely to what they want to do. He is pleasant to be with (more than that--fun to be with), and tells the history or art anecdotally.
And he is MOST reasonable.
I like the idea of LUNCH at the Eiffel Tower--it will take a good part of the middle of the day. It would also get them to the top easier, although you could also give them tickets to get to the top of the Tower, if they don't do lunch.

I agre with Gretchen Michael is a treasure and fun to be with. Hw will also go outside of Paris. We had him for a day in Giverney.