I'm still searching for the perfect draw, but if I am correct, this can put out 77 damage on turn 5 with the perfect card order. All creatures will have trample as well.
This is done by swinging with eight 6/6 soldier tokens, two 7/6 Akroan Crusaders, one 8/7 Anax and Cymede, and one 7/6 Battlefield Thaumaturge.
Going second:
Turn 1: Draw, play Mountain and Akroan Crusader.
Turn 2: Play Island and Battlefield Thaumaturge
Turn 3: Play Plains and Anax and Cymede
Turn 4: Play Mountain, Jeskai Ascendancy and Akroan Crusader
Turn 5: Play Coordinated Assault on both Akroan Crusader, spawning two 1/1 soldiers with haste. All creatures buffed +1/+1 through Jeskai Ascendancy. Follow up with a Launch the Fleet on all creatures. Creatures are buffed an additional +2/+2 through Anax and Cymede and Jeskai Ascendancy. Then attack; spawning six additional 4/4 soldier tokens tapped and attacking. Follow this with the last card in hand, Icy Blast, targeting all creatures on battlefield (including opponents, but not your BFT or soldier tokens), which activates its Ferocious ability. This gives all your creatures and addition +2/+2 through Anax and Cymede and Jeskai Ascendancy. That is how you deal 77 damage on turn 5.
