Chelsea Park was my neighborhood park growing up. I've been there probably 100+ times.
I've played organized and recreational sports there, participated in day camp there, and did about a dozen other things there during my childhood. It's a nice neighborhood park tucked away just off Ambaum and 136th.
The park is basically divided into two sections, the playground area which is on top of a little hill and the field, which is down below.
The playground area was renovated within the last 10-15 years and has a nice playground and walkway area up above. I don't know if it's due to the location, off Ambaum and 136th/near the (formerly called Seahurst Village Apartments) or what, but I don't see too many kids there playing.
The field down below has a small baseball/softball field that is well-kept because it's used for little league baseball/softball and Kennedy Catholics softball team as well. The field isn't by enough for high schoolers (90 ft base paths and 60 ft mound), nor can it accommodate power hitters (due to houses relatively close down the right field line and a moderately short left field. Basically, If you're looking to play baseball you're better off going to Sunset Fields or Moshier Fields - you'll have more real estate there.
The open field/grassy area is though good for pickup games of football, soccer, ultimate frisbee, etc. as well as catch and just general running.
Often, at night - just before sunset ("after work") you may often find members of Burien's Hispanic community playing recreational soccer there - so if you're someone who had the itch to play, and doesn't play organized soccer or can't find people to play with, then it may be worth dropping by one night to see if people are playing.
All-in-all, Chelsea Park is a fairly nice neighborhood park in the Burien-area that provides a variety of different opportunities for playtime and/or rec-athletics read more