Hi Marggy -
<<"When we are there we would like some time to look around Montreux, visit Chateau de Chillon, visit the Queen museum and take the cogwheel train up to Rochers De Naye. Is this possible in one day or would it be too rushed?">>
Steph put it simply -
<<"as it's very individual what's a too long day and what's do-able.">>
There are a lot of things that we don’t know about you, that make it difficult to offer clear advice. I’ll illustrate by how I would plan it for myself. If I were planning that for myself, I'd decide
1.- what time in the morning I want to catch a train (for speed, vs. slower and less frequent, but more scenic boat). We don't know your tolerance for early rising, and how much time (if any) you'd want to spend at breakfast.
2.-As noted by Steph, I'd look at the timetable, and see what train time makes sense based on #1.
On any day, in the morning, for example, there are 4 trains per hour from Lausanne to Montreux, taking from 19 minutes to 29 minutes...longer times are on an "S-Bahn" which is a local and make a lot of stops.
3.- It will take several minutes to ride or walk to Chillon from the main station. I'd check the timetable, which also lists boats. I'd think about starting or ending the day there, so as to avoid delays for changing a train along the way.
4. - I'd thoroughly and carefully study the complete link for Montreux
which includes the one for activities given by Steph.
It gives details of Chillon and Rochers-de-Naye
For example, it says, about Chillon:
<<"No special preparations are needed for a visit to the castle. As most of your exploration will be indoor, clear weather isn’t required. There’s a lot to explore, so a visit will easily take half a day or even, if you take your time and plan some breaks, a whole day. A quicker exploration can be done within 1,5 to 2 hours.">>
For Rochers-de-Naye -
<<"The excursion takes at least 3 hours from Montreux.">>
I don't know how long the Queen Museum would take. I'd do my best to learn how big it is.
Note that Montreux is located on the side of a mountain. It is all up and down. From the lake level of 374 meters elevation, to an upper part of town at Sonzier, at 654 meters, is a rise of 280 meters in about one and 1/3 km. of horizontal distance. Looking around can be an athletic event, or the use of public transport:
5.- In order to put that together, and estimate a time, we'd have to add up those times, make a judgement how athletic you are and what you mean by <<"some time to look around Montreux">> with consideration for your proclivity for walking or riding.
I, at least, do not know the answers to how much time you would actually choose to spend at the locations noted.
Nor, do we know if you wish to be back at Lausanne for dinner...are you on a half-board plan?
6.- I'd determine my return time. What is your last possible return time, based on your personal estimate of how much you can pack into a day and still enjoy it?
<<"or would it be too rushed">>
Too rushed? Or, what other alternative? Not rushed enough? We have posters on this forum who want to pack as much as possible into a day, perhaps so they can say they have been to those places. We have travelers who want every day to be unhurried, with plenty of time to look , take photographs, thoroughly examine all that is available.....
We don't know which kind of traveler you are. ;-)
Here's what I'd do.
First, my observation based on things that I can determine. If I collect the information that is available as noted above, without knowledge of your preferences and "style," it is my opinion that it will be a full day, and could be stretched to a day and half or two, depending on your choices.
So, what I'd recommend is that you look at a map of Montreux ( remembering that it is hilly), rank the events in terms of your priorities, put them on the map to guide your time estimates, check transport times, and draw your own conclusions. You can always drop an item off the end of your ranked list.