Not sure about the fee, and not sure what the current behavior for change should be may you use a segwit address without specifying a change address.. so to guarantee that you get your bitcoin's change back in a segwit address, simply create a receiving segwit address and enter that address in the options (see "custom change address"), after enabling "Coin Control" feature:

https://bitcoinspakistan.com/files/2014/03/coin_control_enabled.png

This way you will do exactly what you want to do.