I'm not quite sure what you're asking. Are you looking for activities in Portland/Vancouver, Astoria, Seaside, Seattle, or where?
Astoria is about 90 miles from Vancouver taking I-5 to Kelso/Longview and crossing the bridge there. Seaside is about the same distance, except you'd go into Portland and head west on hwy 26. Between Astoria and Seaside, I think your children would prefer Seaside, where there are many attractions geared towards kids, and most are handicap friendly.