As alelks said, it takes a special woman/family to be with a man who is in the military and one that can work this out by her self in a marriage when you are in Special Forces.
For me when I'm home, you have to make time to be there for each of your kids. Each to their own in their ways of making it happen. My son isn't into shooting guns, but I drag him out with me on a weekend for father-son time. My son, like every kid I feel, plays his Xbox. I suck at it, but every deployment I work on my gaming skill to play with him at his first person games. Deployments, we (SF) have it best, so you can talk to your family for free typically, internet at firebases, and sometime, not always you can video chat. With your kids and school, my daughter has my brain, not the best personality traits
So when she is having issues with school I will email her teachers or even call them up so I know WTH is going on. My wife works and it is hard for her to make a pareant/ teacher conference while I'm deployed. Email works and I have never been turned away on a deployement, teachers know because of your kids. If your school doesn't have a after school tutoring services, then you need to ask the school or teachers for the help and who (Teachers) provides any tutoring services. This way if your wife doesn't know a subject, you will know what teachers do at home tutoring services in the evening or after school.
Being married, that is different for each person. For me, The wife and I will take a trip for a long weekend (Fri, Sat and Sun) by ourseleves. She will tell the kids slepp over at a friends house, she talks to other pareants about the weekend plans we have and most parteants know the deal and will help out. Go to the beach, mountains, a major city for a music group concert, whatever. Get away by ourselevs to have fun like dating or talk things out away from the kids. Just like when I'm deployed we will skype when the kids are gone to talk about issues we don't want them to hear. Once again your time management skills are at play. But your wife has to be able to live on here own; do the bills, run the kids to sporting events, cook meals, all household chores, in-laws issues/drama, etc.
As far as training for SFAS, you have to do that early in the morning, during the daytime or late at night or weekends IMO. When I'm getting ready to deploy, I throw on my kit or pack and hit the streets and trails around my house after my kids are asleep or get earlier to do the same thing. Your time management, just like anyone in life, school/college, etc is what makes you find the time. You have to know how to use your time, just as when you finially make it into SF or the military you'll have to deal with these "things". SF wants "External motivation" people, DOERs not WAITERs, thinkers. Your wife wanting you SF.. Humm.. anyways then, she needs to pick up when your not there. She will be doing it when your gone on a deployment. If your joining as a 18X, it will be a big eye opener when you go off to basic for her. She needs to know how to do things NOW, while you're there, if she isn't already. Get her on some 25 meter targets, if she doesn't have any now.
My wife has been with me since before I went to selection as my GF and married to my crazy @$$ for 15 years, 18 years total. Just my point of views.