If you want to follow-up the idea of Cultus Lake:
https://bcparks.ca/cultus-lake-park/
I've stayed in Delta Grove, and here are some notes:
-No hookups
-there is a single dump for your tanks at the Maple Bay site, $5 to unlock the dump-lid
-Chilliwach and Escape are not too distant
-Escape showroom has had a 5.0 in there for several years; I last saw it a couple of months ago
Cultus Lake is within a stone's-throw of 3million people (Greater Vancouver) and is filled in the the summertime. You can search and check (cancellations do happen; single-nights are more-likely); select "Cultus Lake" in the first drop-down:
https://camping.bcparks.ca/
Good luck!