Oh honey I know what you are talking about. Our entire families live here in town. Nobody is further away than 15 minutes. The great grandparents lived right up the street till they passed away.
It is a blessing and a curse.
Now that your children are getting older and will have full schedules, it is time to set up your family calendar and stick to that. If (and with your permission) others want to see you all they can join you in these activities.
We tried to attend all birthday celebrations and of course large holiday gatherings. We then would send out an email to everyone letting them know about weekends we were not available and then a list of activities and events we would love for family to join. We would try to suggest that if we attended a childs sports event, maybe we could all go to an early dinner somewhere.. Or if it was a school holiday we would suggest a family day on these special days..
I also explained that SCHOOL was our daughters top priority and if she had important homework or projects, we would not interrupt this time. Everybody agreed with this and it taught our daughter how important her school work really was.
When our daughter was invited to a friends bday party, that was usually her priority over a family event that was not of a large significance. This was negotiable at times..
We saw plenty of family during the holidays and summer also to help them feel like we were spending as much time as possible.
As long as you attempt to participate in a fair way, it is up to the other family members on how they will react. My MIL would always "forget" what year we would be at her home for Christmas Eve! Drove me nuts. And with a husband who is ADHD and no sense of dates or times, thank goodness our daughter could back me up on those occasions..
Just do your best.