Well, I always brace for this time of year. We have 5 family birthdays and Mother's Day in a span of 5 weeks. Then, yes, all the end of school activities, extra recitals, etc. I also teach music at night, which means I also have to be on for my students, as well as my family.
For us, each child is only allowed to be in two activities at once. But over the course of the year, it adds up.
Also, I'm DS's den leader. We meet twice a month. And, actually, we are only meeting once in May to help reduce the amount of crazy end of the year stuff.
I don't know how often your girl scout troop meets, but it seems like around here, they only meet once a month. I know a mom who is a leader, and they often pair up a few families to lead a meeting.
We don't do playgroups/playdates. Maybe it's different for us, since we don't homeschool, and I was born in the 70s, where you either roamed the neighborhoods or learned to entertain yourself. My kids, on average do something with their friends once a month, excluding birthday parties.
For our family, I do two birthdays-one with family and one with friends. I do it for many reasons.
We do not have the money every year for birthday parties at places. This last year, I declared an "at home birthday party year." Due to finances. (Otherwise, between two kids, I was looking at dropping $400 just on birthday party expenses.) We've hosted grand parties at our house. Very simply ones..going to the park, coming back and having snacks, and then water ballon fights/water play. We've had kids that have cried/hidden at our house when it was time for them to go.
I protect our weekend time. Kid activities are done Monday-Friday as much as we can. My kids need down time, to stare at the clouds, etc.