We have stayed on a number of occassions at the bellvue au Lac.
It is a member of Best wester, but family run.
Very clean and friendly.
directly across from lake and a nice walk to Centre.
that was with our two kids and my wives parents
Clean comfortable and child friendly.
Also, not sure if you going in the Summer but they have an outdoor swimming pool.
one step up, we have stayed at Lido seegarten.
this Hotel has had mixed reviews, but we always found it friendly and clean, but Rooms a bit tired.
Directly on the lake, kids love it. Expensive restaurant but fabulous choice on Menu to suit all tastes moods and most especially for kids.
Another step up, villa Castagnolia, 5 star , could not recommend it highly enough. great lake views from rooms { circa 500 metres distance}
Hope it helps. Have not stayed in the two you mention, though I know both to pass by.