Welcome Lisa,
I was also a SAHM to my 2 children, who are now 18 and 22. I did not homeschool, but was very active in their schools and outside activities all throughout their years at home. I, too, did not have parents who took any interest in my life and my father spent most of the time criticizing everything I did or said. Consequently, I did not have a good relationship with either of them and they both died with little concern from me. I vowed to never be like them and to give my children the love and attention that I never had.
Both of my kids are doing great and we have an excellent relationship (despite their father having bailed out of our marriage after 22 years). I agree that being there in the background is important and you certainly do not need to, or even should be around 24/7. They need to develop their independence without you hovering over every decision and choice they make. They will make mistakes and hopefully learn from them. However, I rarely missed a game, meet, choir performance, or award presentation, and I know that they appreciated my support. I still travel to enjoy their college experiences when I can.
At your kids' ages, finding games you can play with them, sports you can do together (we loved skiing as a family), visiting zoos and museums or anything that gets them talking and interacting with you, is fun and exciting. I think carpooling your kids on a regular basis and just listening to them talking to their friends can be very enlightening.
Just enjoy them as much as you can, because before you know it, you will be like me with a big empty nest. It can have its' benefits, but also can be very lonely and quiet.
Brigid