I’m sorry you’re feeling so shocked and lost. Is this the first time he’s deployed for any length of time? You will be fine and it will go quicker than you imagine it will. Will he have any leave during the six months?
Practical stuff - ensure you have his service no, his contact /postal details, emergency contact route. Find out how often he can contact you and by what means. Work out a schedule for that (eg around time difference or school and work schedules).
Your kids are not tiny so that helps a lot. Do they have any additional needs? Make sure they are pulling their weight around the house (in an age appropriate way) so it doesn’t all fall on you. They should be doing that now anyway of course.
what does he do now that someone else will need to - eg school run or particular bits of household tasks. What can he get on top of before he goes eg house maintenance or repairs if that’s his area.
make sure you’re the named contact on bills eg broadband or tv license so that you can manage that stuff.
Do you have childcare available so that you can have a regular bit of hobby / leisure / socialising time for yourself each week, or is your 14yo ok to manage themselves and the 9yo for a couple of hours if needs be?
Can you book a family holiday for Oct half term or take kids out of school for a week in Nov even so you have something to look forward to.
Break it down into a week or month at a time and it will feel more manageable. Plenty of people manage a family as a single parent - and you’re not a single parent, you’re just shouldering the admin and household burden solo for a short while.
you’ve got this. Do you have forces friends you can lean on a bit?