I'm taking my elderly parents next month and we'll be in Paris for 5 days.

I think they'd only be up for one daylong trip out of Paris. They'd probably like the gardens a lot but of course Versailles is more well-known.

Now if Giverny wasn't as crowded as Versailles usually is, it may be a more pleasant trip for them.

Though come to think of it, the sheer scale of Versailles will require more walking for them too.

Good tip from bookseller05. We have used the "découverte senior" fare several times. Here's the information from the SNCF:

http://www.sncf.com/en/reductions/seniors

Well not sure if this will appeal to you but we did a bike tour that went to Giverny, I think thru Fat Tire Bikes. We took the train as a group from Paris, went to a market and bought food for a picnic at Vernon, then biked to the garden. It was very pleasant.

We also visited on another occasion in the fall when the dahlias were out - wonderful! Do pre-buy your tickets - easily done online for a small fee and saves you waiting in line at the main gate. Enjoy!

Monet fan here. Husband, niece and I went in May 2012 to Giverny via train (prepurchased tickets) and the shuttle bus. We took the first train there and were on the first bus. We prepurchased the entrance tickets so went in through the group entrance, no one else in line, but I steered us wrong and we ended up in the museum instead of the garden. It worked out well because there was a torrential downpour while we toured the house. The rain had pretty much stopped when we were done and ready to tour the gardens. Yes it was crowded but so very beautiful that we all loved it. The next day we toured L'Orangerie and that was incredible after having seen the gardens and house.

We took a minivan tour to Giverny and were glad we did. It was a very relaxing day! It was more like an SUV with only five of us plus the guide who drove.
And, oh yes, Giverny is magnificent!

From what I calculate, the minivan tour uses their 5 hours with 3 of them being the drive there and back.

I didn't time how long we stayed there, but we had plenty time......more than enough time take about five rolls of photographs!
Further, the day we went, there was an accident along the way, so the driver/guide graciously let us stay longer that the usual departure time for the return trip.

We took a picnic the day we went to Giverny, and sat in Le Jardin d'Eau just opposite Giverny. It is a beautiful place and its not just a garden, it is a little slice of magic!!