It's okay to vent, that is what we are here for! :-)
Work is work. Your real life is when you get home, being with your family and friends. Sounds like you have a lot of immature people who work with you, as well as people who are just not like you in personality. There are many other places you can befriend people. Try joining a M.'s group (there are even groups for working mamas) at www.meetup.com, or at a class or volunteer service. Believe me, it seems that way, but there ARE a lot of moms out there just like you, who want to meet other moms but are often shunned and left lonely.
I also work, but full time. When my daughter was younger, I also tried meeting people at my work and it just didnt' work. My coworkers are nice, but they just were not people I'd hang out with if I met them on the street or something. I've joined some moms' groups since then, met some nice people, but I still feel lonely and wish I could meet more moms. However, like you, I am grateful for my job, which is light and allows me to get home to my little pumpkin by 4:30 pm daily, no nights/weekends.
It's not my ideal job, but like you, I am at a point in my life where my home/family life is more important than what I do at my job. I could go for a higher paying job with better coworkers; it would mean longer hours and more stress. But now is not the time. Now, to me, is spending time with my daughter and husband.
As long as I have my job, my benefits, and flexible schedule, that's enough for me, as for you.I wish I had more friends at work to keep me occupied during down time, but heck, they are just not my type; my REAL friends lie elsewhere.
We can't change the way others behave; we can only change ourselves. So in your case, do what you're doing! :-D Continue to be happy about your job, shrug off those superficial/immature coworkers, and be assured, that your REAL life begins the moment you get home and are surrounded by real people and family who mean to you. :-)
And screw that party -- why go to a party where you don't feel welcome and part of the team? Time is a precious, indispensible factor to you, and spending time with people who mistreat you is unecessary.