You are blessed to have a homeschooling group through your parish. As the children grow older sports, music and other activities are going to interfere with this group getting together. I see the same thing happening at our lovely parish, with our older children filling our calendars. So, I understand the lonely feeling when the families participate in older children's activities.
I have three suggestions for continuing your group's companionship. First, try to attend Mass at the same time. Whether it's just Sunday morning at eight o'clock, or every Wednesday morning while some of the children altar serve, try to be there. Perhaps the children can play after the service and you can catch up with the moms at a close house or even in the parking lot.
Secondly, plan a couples night out at your home for the homeschooling families, or invite the moms over one evening for a game or group discussion. Maybe a book club that meets once a month, at the most? If you are concerned about the moms feeling overwhelmed, a once a month commitment isn't hard, and not everybody has to make it each month. An hour walk in someone's neighborhood might even be a fun way to visit every once in awhile. My husband reminds me, often, to not be afraid to be the one to initiate the social event.
Finally, if you have a homeschooling co-op within an hour or less of your home, you could try to attend their meetings. Perhaps there are a few moms outside of your parish that you may get to know better. Of course, if you are like me and you live a ways out, that may not work. I noticed that you have been homeschooling for quite some time so you have probably already explored that option.
By the way, the other night I went out to dinner with two former high school friends that I have known forever. One friend works full time and the other stays home with four children, but sends her children to school. It was wonderful to get a different perspective from these moms, too. I was reminded that no matter what type of education you choose for your children, that there are challenges. Sometimes moving outside of my homeschooling group recharges my batteries, too. However, the encouragement is what I need most from moms just like me.
Hopefully, these suggestions will be of some help.
Blessings to you and yours,