Small spelling correction: the train goes from Martigny in Switzerland (in the Valais) to Chamonix and on to Saint Gervais les Bains.

I don't know how much walking you want to do. Here are some suggestions:

Cable car to Aiguille du Midi -- spectacular views in all directions. You can look out over the glacier to Italy (and the gondola spanning it). Actually two cable cars with a changepoint at Plan d'Aiguille. From there one can walk to Montenvers -- the top end of the cog train -- in 3-4 hours but that's likely more than you're seeking. The walk is largely level along a "balcony".

Gondola / cable car to Le Brevent, with an intermediate point at Planpraz. Fabulous view from the top, with some possible gentle out & back short walks. Don't know about wildflowers. We were up there the first day the cable car was running for the summer & there was snow at the top.