10 am isn't early for Venice. 7 am is early, and I always caution people about that.
No, for such a late start, I'd stay in Venice.
The airport hotels are focussed on the airport, not Venice.
Where in Venice would you like to stay?
The vaporetto runs all day, and the day schedule starts around 5 am. Are you going to be on a direct flight home or is this a connecting flight (more likely) via another European city like Amsterdam, Rome, Paris, Frankfurt, London? If the latter you don't need to be at the airport ages before flight - maybe 90 minutes, unlike flights to the USA.
If your hotel is convenient to the vaporetto stop, I'd hop that around 6.30 or 7 after breakfast, a nice empty vaporetto (people are mostly coming in, some will be leaving), down the Grand Canal one stop beyond the Ferrovia, train station to the Piazzale Roma and then the airport bus from there. Fastest and cheapest.
Don't worry about the train when going to the vicinity of the airport - it doesn't go anywhere near.
I see that you've been visiting Venice for several years. Where do you like to stay?