Double Booking a single venue for childrens Party

Being a mom is always a proud moment especially when celebrating your loved ones big day Birthday. We booked the venue at Nitro Park Bowling party venue in the new amazing Bay West Mall. I sent out invites with the times and dates to all our friends and families. The mall is just outside of Port Elizabeth so its quite a drive to go there. All was confirmed I baked the cake and catered for all invited and then some! Pulled out all the stops to make it a memorable day! My husband and I arrived at the venue with our guests hot on our heels and when we were ready to set up the lady that took the booking told me to move my party from 1 pm sat 25th July to 3 pm. Now we had friends already on their way it was storming weather and I must stand there only to see another party happening in the venue. How can i tell 30 Parents to please go back home and cone in 2 hours later! When we asked to speak to a manager we were told there arent any but here is a R5O gift voucher to show we are sorry. That voucher would only have covered the entrance for one child to bowl!! We ended up having to have my daughters 3rd Birthday Party in the Bar area of the Nitro Park I was so ashamed as that is wrong!