It will all work out - it's just the shock of it all and the destruction of the schedule you had in your head.
My husband was not deployed, but when our kids were little he was NEVER home when there was a crisis. The pipe in the attic above the kitchen sink got a hole in it and it was raining in the kitchen from that pipe. Husband gone.
Son had a reaction to polio vaccine and ended up in Texas Children's Hospital with paralysis (temporary!). Husband gone.
That sort of thing.
Invite that SIL! Call in all hands! Good luck!