There's a sense of ambition in the logline - plus a sensible page count - that made me open this and flick to 10.
The writing flows well, your dialogue is good and there's clearly skill at work here. BUT there's so much going on. In the first 10 pages you introduce us to three distinctive alien races, two planets, at least two potentially meaty character arcs (both to do with grief, though that's fertile ground so not in itself a problem)... it's a lot to take in. Too much, really. It's hard to keep track of who's who.
Also, structurally it's a bit odd to show the beginnings of an invasion, then cut away for some teenage angst and subaquatic high- (or is that low- ?) jinks before returning to it on page 12. When the violence started in the forest I thought 'here comes a sequence' before we were not only elsewhere on that planet, but suddenly on a different planet with a new set of characters entirely. Your tension immediately disappates. Perhaps move the actual landing scene on 3 to the other side of the Altantan scene, so it's one continuous attack? The time jump is also not great for tension, why land during the day if stealth is the objective, why not wait until night? The farmers could be night-farmers (another observation, your aliens are that funny mix of being not human but a bit human, everyone talks in English, is fairly humanoid and do 'people' things) farming some strange luminous crop, before the Kierans (which I'm guessing you know is also a fairly common Irish boy's name) carry on towards the village.
I sound a bit down on the script, but I'm not - from what I've read I'm impressed with the skills on display, and if you check in to let me know you're here I'll read more. I'm just wary that you don't so much build the world as plunge us straight down into it, without an audience surrogate character - Jake from Avatar, Neo from The Matrix, Elizabeth from Pirates of the Carribbean, Luke from Star Wars, Frodo from Lord of the Rings - who's learning about it at the same speed as us. Those characters are very useful, as they can ask the questions we're thinking. Not saying you have to have one, and maybe one will appear, but the first 10 pages are currently a dizzying array of characters, plot and settings.
Still, you two can clearly write. Let me know if you're about.