Looking at eBay sold listings, secret rare Ultra Balls go for around $150 to $200 in Near Mint condition. If you could post some pictures, we could probably help you evaluate the condition.
(By the way, I find it awesome that you're playing with your family!)
Thanks for your help. My kids and I love playing games. TCG, video games, etc. Surprisingly, they are teenagers now, glad they still enjoy it.
I attached a few pics. I have a bunch of other stuff, ace specs, full arts from the plasma stuff. Not sure how much people want the cycled cards.