Single engine pilot reported an NMAC with a glider while in contact with ATC for flight following.

Narrative

I flew with my husband and son from ZZZ1 to ZZZ-ZZZ2-ZZZ3 on a beautiful VFR day. I did not file a VFR flight plan but had flight following throughout my trip. About 5 to 10 miles north of ZZZ I had descended to 2000 from 5500 to get ready to enter the pattern at 1000 (left downwind for XX). I was flying with my autopilot on. There was an aircraft at about 1000 feet and overlying the ocean that was on my Foreflight but not visible visually. There was no other traffic in sight or on Foreflight or advised by ZZZ Approach. Suddenly my husband who was the front passenger pointed to an aircraft that was just below us and towards the right. The aircraft descended and landed in a field according to my 16yo son who was my back seat passenger. I must've been within 50 feet of him and had no indication that there was a glider or a tow aircraft on ADS-B or through flight following. I was too shaken to tell approach what happened especially since it was starting to be a heavy workload time and I had to get ready to land shortly. The rest of the trip was uneventful. On our way back from ZZZ3 to ZZZ1 at the end of the trip approach was warning other aircraft of gliders though I didn't catch the location. This was terrifying and put my family at unnecessary risk. I think it's unacceptable that gliders are allowed to fly without any ADS-B out over high traffic areas.