Yes, Copper Creek is the DVC section within the main WL building, but none of the DVC rooms have CL access.
I get your disappointment. Unfortunately, "Club Level Access" is the case in many of the resorts - CR, Garden Wing Suites, GF Outer Building Suites, some of the Suites and deluxe rooms at BC, etc. They all have access to the lounge, but are on different floors or, in the case of GF and CR garden wing, some rooms in completely different buildings We once stayed in an outer building suite at GF with Sugar Loaf access and never even went to the lounge (not our most cost effective trip!).
If not being able to send your kids to the lounge on their own is a deal breaker, you may want to switch. My DS is 11 and, just being the kid that he is, I wouldn't feel comfortable sending him alone at this particular time. If you would feel more comfortable all going together and it fits into your schedule, I would think about keeping the reservation. We stayed WL CL in a standard room last year (7th floor) and it was amazing. I tried and tried to get a WL CL for last December and couldn't get it. We ended up in a 1-bedroom villa in Copper Creek and it was stunning. I just ended up stocking that fridge with things we would have had in the CL lounge. WL at Christmas time is absolutely gorgeous.
If you ever want a better idea of where rooms are located at each resort, Touring Plans has a "Room View" finder which, while not always completely accurate, will typically show you where the CL rooms and suites are located.