We are a family of four, kids aged 7 and 11 and visited Lausanne for work and vacation. The apartment worked very well for us and there was more than enough room for us and all our things. You will have to use transit to get into the city and down to the waterfront. We walked from Ouchy (the main port) one day and it took 45 mins with a very steep climb that our kids did not appreciate. Transit is easy to access and punctual so it's simple to get to town or anywhere else in Lausanne. The apartment has laundry facilities which worked well and there is a reasonable size grocery store a 5 minute walk away (but be warned that grocery stores close at 7:00 PM are not open on Sundays).
It's a nice apartment in a beautiful part of the city. There is a small park nearby that our kids enjoyed. And Frederique is a very generous and friendly host - any and all questions we had were answered right away.