Lido at low season can have some good bargains
I would stay at Lido and take the No.1 to Venice Proper than stay at Mestre.
Early Oct we stayed at Lido - a nice little hotel just 7 minutes walk to the ferry dock, at 80 euro incl a very decent Continental breakfast (boiled eggs and pate were among the many offerings.)
I am guessing the rate would be lower in winter.
No.1 runs very frequently and in 10 min you would be at San Marco.
No way we would stay at Mestre when visiting Venice.