The various petty JW rules and regulations regarding what is / isn't allowed during weddings would make the Pharisees blush. The irony is that most of the rules were made up by Fred Franz who was never married. I'm assuming he wasn't a big fan of rice and confetti , but enjoyed cake.
I was in roughly a similar situation ( attending a non-JW wedding where many of the guests were JWs ) and there was a toast , but it was pretty late on in the evening by which time many of the guests were already a little tipsy anyway and even a few of the JWs happily "toasted".
It's your day and it isn't a JW wedding so I would just do it.