Families flock to Fort Stevens State Park [1] (reservations 800/452-5687, year-round, $21 tent camping, $27 RV camping, $41 yurt, $6 hiker or biker). With over 500 sites, the campground is the largest in the state park system, and it’s incredibly popular. The park’s many amenities and attractions make it the perfect base camp from which to take advantage of the region. Just be sure to avoid spring break (around March 23–29) if you want to be spared the rites of spring enacted here by Oregon [2] teenagers.
Across the road from the state park, Astoria Warrenton Seaside KOA (1100 NW Ridge Rd., Hammond, 503/861-2606 or 800/562-8506, $31 tent, $33 electric hookup, $48 full hookup, cabins $62 and up, $5 resort fee required) is another sprawling campground. Amenities include an indoor pool and hot tub, a game room, miniature golf, and bike rentals.
Links:
[1] http://www.moon.com/destinations/oregon/north-coast/astoria/sights/fort-stevens-state-park
[2] http://www.moon.com/destinations/oregon