Child care is tough no matter what you're doing. We run and mountain bike . . . so the race seasons are a little different than Cross. As much as I want to get into mountain bike racing and do the local race series, I can't race that many weekends so close together because of the childcare issue. Right now we keep our racing to "bigger" events.
We pick out about 3 big races in the year we want to do together, usually spread out over the year. Then we ask relatives to watch the kids for that entire day, or over night that weekend. Racing takes ALOT out of us and we've found that if we are both racing, neither one of us has the patience or energy to care for the kids.
We will also pick out 3 or so different races so we can watch the kids for each other. We do wish we were both racing, but that's just life for us right now. If there is a race we both really want to do, we'll alternate years.
I do think talking to some of the other local racers or event planners about babysitting is a good option. I actually started volunteering with our church youth group, I have to admit, partly to find babysitters!!!