Someplace I read that Emirates is offering great prices for flights into Milan to increase their business. Other airlines have to follow suit to remain competitive.
I would absolutely fly into Milan to save $2800!!! The train from Milan to Venice takes only 2 3/4 hours. You can use this time to rest after your overseas flight. the main trick is timing the train trip if you want to benefit frommthe low fares for advance purchase on your train tickets. The Super Economy fare can be as low as 9 euros but is non-refundable if you miss your train. You might look into family fares, depending on the ages of your children you may qualify. Make sure your tickets are to Venice Santa Lucia, not Meatre.
Flying into Venice has its own issues in getting to your hotel frommthe Irport. The Alilaguna takes about an hour and tickets are now 17 euros ( more than the train from Milan to Venice. But plus vaporetto is cheaper ( I think a combined ticket is around 12 euro) but you have to change from the bus to the vaporetto, a hassle with luggage.
If your return flight from Milan is early enough that you need to spend a night there, don't disparity. Milan is actually quite enjoyable, especially around the Duomo and Galleria, and the pedestrian zone on Via Dante.