You need a wilderness permit to camp overnight in the backcountry. period.
You don't need anything to dayhike.
When you are there just go to the Wilderness Center and talk to the
rangers there. They can give you more info and reiterate the rules, etc.
I'm not sure what you mean by
"take only a small pack up to the destination"
since you will probably want
-food
-tent
-stove
-sleeping bag
-extra clothes
but I guess you could get the boyfriend to carry all that ...
Since you have a campground you can easily get a permit for the next
day for wherever you want to go. You'll just want to show up
early to the wilderness center.