Pay for one person for two days to confirm your permit. You might even be able to just pay for one day. Add people and days to your permit as the trip approaches and your plans solidify. I believe you have until 3 days before launch to make changes, but I may be wrong. You cannot add people or days at the launch site, at least with the 4 rivers lottery.
I'm not happy about being over the hill, but I am grateful there wasn't a cliff at the summit! - Frank and Ernest