[X] Take up full defensive formation, give the Beastman a bloody nose and then retreat in good order.
We're not going to be moving anywhere near as quickly with the full group as we could alone, so attempting to run for it just means we're getting hit while we're either trying to organize to leave or a confused mess in travel formation.
For the write-in, I'm deeply skeptical of the utility of the scratch fortifications and outright opposed to the elemental summoning. We're dealing with a strung-out and almost certainly numerically inferior force that's already having morale issues while having supremacy in ranged weapons. Shock value of unobstructed fire would be reduced and given the very short time window maneuver time would be better spent getting our troops in order. For the elemental summoning, we're neither in a position where we're in desperate need of any edge we can get nor on the absolute home stretch. Summoning them, let alone in the quantity specified, will tank our endurance going forward and, crucially, will prevent us from, you know, properly organizing our forces and fully updating them on the situation/plans in the scant minutes we have, especially if we're simultaneously trying to get a bunch of non-combatants to set up some barricades in a manner that breaks up their charge and funnels them where we want them but doesn't provide them with significant cover AND get said non-combatants out of the way before things get hot.
Like, if we had half an hour or twenty minutes to dot our i's and cross our t's I'd be 100% down with the quick and dirty field fortifications (even if I remain entirely opposed to gratuitous spellcasting), but right now they open us up to getting hit with our pants down, are unlikely to be a critical factor in swinging the battle to (or further to) our favor regardless, and done improperly they'd be an active hindrance in the coming battle.