My 2015 passenger van has the rear heat option which blows very hard across the floor just aft of the first bench seat row, that may not have helped you much anyway if you only have kids in the first row (can still take a while to heat the whole rear cabin from the back). Something I noticed right away though was very disappointing floor heat at the driver/passenger front seats, as others have said, like my feet are being coughed-on by a mouse.
I read a past recommendation elsewhere on the forum which did help, maybe you can get some more air to the rear seat. The air diverter flap behind the dash never stops allowing air out the mid-level (steering-wheel height) vents, regardless of the position of the air level/height knob.
So if you turn the knob to upper/defrost, some air comes out of the defrost vents and a lot comes out of the mid vents. If you turn the knob to the floor, some comes out of the floor vents and a lot comes out of the mid vents. The mid-level vents need to be closed, or mostly closed before the floor or defrost vents in my van blow very hard. It's still the weakest floor heat of any vehicle I've owned to date, but the above did help a lot.
Something else to watch out for is the two vents on the upper front-edge of the dash, just to the sides of the center stack or storage bin. These seem to blow fresh outside air (could be useful depending on cargo) which is not heated at all. When I got my van, these were about half-way open and I drove it for a long time like that before I figured out that they have a different air supply.