Wedding vows question?

I have a problem in that we are writing our own vows and I want to say things like "I promise that.... forever" but my parents (who are divorced) will be at the ceremony and I feel like my dad will be cynical about it. I am even cynical about it because I know the statistics. Should I SAY forever even though I know that it might very well not work out that way? I want us to be together forever and we are a good team and I think we can make it BUT I realise lots of couples think this at the time they get marrried. What to do?