not being an arm-chair general...
Lots of "tactics" here, but here's a couple thoughts to plug into any "plan":
1. Ammo - you have miscellaneous calibers - they have AKs - one ammo.
2. Is the river fordable without the bridge? If so blowing the bridge is not battle effective.
a. it is a faster path for your saviours to enter;
b. it presents a narrow (and reasonably controllable) passage to your enemy. Controlled and manipulated (tactics), you can off a bunch of BGs and with heavy small arms fire and drive the remainder back to regroup (and rethink), then you can recover many more AKs/ammo needed to arm your "veterans" et al. Face it - store owners won't keep up with the firing rate and you'll have nothing but unusable cartidges left (to throw at the BGs, huh?).
Take a leaf from "The Patriot" - use the trees and other cover to trim the march down to reasonable numbers - after all, they are strangers - your folks know the terrain. Don't charge the field - they are (I suppose) trained soldiers. They are also limited to what they carry. Make it hard to get potable water. Consider burning the crops if any but only after the fields no longer provide you cover.
There's probably more, but I'm weary now.
Have fun. Let me know who wins ok?
FWTV - For Whatever The Value
...When seconds count, most help is just minutes away.