We have always wanted to stay there and we are a family of 5. Does WL sleep 5 without getting a very expensive room? Just want a standard room.
Assuming you're talking about the resort side (not the DVC side), then no, the standard rooms only sleep 4. The only other option is a Deluxe Room, which sleeps 6.
Renting DVC points or booking via a cash reservation on the DVC side (technically Copper Creek Villas & Cabins and Boulder Ridge Villas) will give you more room/accommodation options.
Boulder Ridge studios allow 5 with the pull down bed. Copper Creek does not.
At Copper Creek, the smallest unit that sleeps 5 is a 2BR. Even on points, it will be pricey.