I also have the stipulation for my entire family when on trips to big meets that I will do nothing I don't feel will benefit my performance. My wife understands and my family understands because I openly talk about it. I liken it most closely to "hey I don't barge into your most important presentation of they year and demand you go on a hike at that moment" it works because they are on board with what I do.
On the other side of the coin I try my best in the off season to be with my family, I go on vacation with them and try to focus time on them. It has become very balanced. From the outset it will be much easier if you talk to your significant other about it as early as possible. If they aren't on board, it will be extremely tough, I promise. I know that Reese, Adam, Christian, and Cory all have very supportive wives/families.
Last summer my life got a whole lot better and more complicated when my son Charlie was born in June, 2 days before Rome Diamond League and 3 weeks before US nationals. My wife and I knew full well going into it that it wouldn't be easy. I didn't go to Rome, even though it would have firmed up my Diamond League points lead, I wanted to be home with my son and help my wife out.
We knew that three weeks later I had to go qualify for Worlds. My wife was wonderful about getting less sleep in those three weeks (and beyond) so that I could get more and perform well. This went on to Moscow, I was gone for a month of the first three months of my son's life. It was hard for me being away, but even harder for her at home getting used to being a mom. She let me get ready for Moscow and when I got 2nd and was disappointed she supported me unconditionally.
I cut out a few meets at the end of the season because I felt that I had already put myself in a position for the #1 world ranking. After my last meet in Brussels I spent a month and a half just with my wife and son. It is a balance, and it really is all about communication. I am gone roughly 100 days a year, but when I am home, I am present, and try to help. I am very lucky in that this is my only job and that where I train (PSU) is extremely flexible.>>
As I type this I am sitting in Frankfurt airport for my first trip of the year, I miss my family, but I also know they are behind me 100%.>>