A Change In Topics-Feeling Unwelcome

I know my posts up until now have been about cooking but I felt the need to vent. For the past few weeks, we have been taking the little man to a local kids gym for a sports class on saturday mornings. He loves it. It's a small group of kids his age and each week they are introduced to a new sports skill and color and activity. It's great that after a busy week we can spend 45 minutes of uninterrupted time dedicated to him.
This gym we take him to also has "open play time" that is available all week. Today was the first opportunity i've had to take him to open play since we joined. So, super excited to spend the afternoon with my boy, I picked him up early from daycare and we were off. There was a class going on when we arrived so the gym was almost empty except for a mom and 2 little boys. The employee at the desk greated us very nicely and told us to have fun. Thats where the friendliness stopped. Little K and I entered the gym and were immediately stared at by the mom(who was playing on her cell phone btw). She actually got up and ushered her boys to the complete opposite end of the gym as soon as K started playing near them. Ok that was weird, right? But whatever, we kept playing. He was having a blast. A young female employee then came in and said hi and asked how old he was. I told her 20 months and she made a face and said "oh". And then walked away. Seriously? Ok..just keep playing mom, don't think too much of it. At this point the class let out and those kids all came into the gym. With their moms and 2 more employees who appeared to be managers or higher ups of some sort. This is where I suddenly felt the need to leave. Not one person acknowledged my presence, or my son's for that matter, not even the employees. They started pulling the kids around on wheelie things and almost knocked him over twice, no one said a word either time. They all seemed to rotate around the room away from us, making faces and staring the whole time. I know I can be hyper sensitive sometimes but this was definitely not me making it up.
Little K and I put our shoes back on and headed out, both feeling confused about why we had to leave. It had me thinking the whole ride home. I felt like such an outcast because I'm not able to be there during the week on a regular basis and these moms seemed to have formed some sort of club with exclusivity to stay at home moms. I felt like I had a giant sign over my head that screamed "working mom-please avoid me!" I just don't get it. Stay at home mom, working mom. Doesn't the word "mom" mean the same thing either way? We are all just trying to do the best we can for our little ones, right? Believe me, I wish I was fortunate enough to stay home more with my son but I work out of neccessity to support our family. It's frustrating to me that as women we are so quick to place labels and judge each other about the way we parent. We have enough battles to face in this world, shouldn't we band together and support each other instead of making one another feel lousy about the choices we make?
I know one thing for certain, I'll be sticking to K's normal Saturday class until the session's up and we won't be renewing our membership there.