As an officer how much time do you spend away from home/children?

This is entirely dependant on your role and which Capbadge you commission in to as some deploy more than others. If you intend to live in a military housing with your family then you will likely be able too go home to them most nights like a normal 0800-1700 job as you will be based near camp. The exceptions to this are of course if you are deployed or on exercise which could be just a week or up to 8 months (unlikely) away from home. Your family situation will likely be taken into account with regard to where you are posted to ensure the best output from yourself. If you own your own family home that you would like to continue living in then you could either request postings which are relatively close or you could choose to travel back most weekends.