fi.wikipedia.org/wiki/Seattle_(p%C3%A4%C3%A4llikk%C3%B6)

The location is misstated.

Authoritative Washington sources place Blake Island in Puget Sound, not in Elliott Bay:

• Washington State Parks says Blake Island Marine State Park is "located in the heart of Puget Sound."
• HistoryLink says Blake Island "lies in Puget Sound" and is "between the south end of Bainbridge Island and the north end of Vashon Island," about four miles off Alki Point.
• HistoryLink’s article on Alki Point says Alki Point forms the southern boundary of Elliott Bay.

Putting those together, Blake Island is outside Elliott Bay: it is west/south of the bay boundary, in central Puget Sound between Bainbridge and Vashon islands. So describing Chief Seattle’s birthplace as being on Blake Island in Elliott Bay is geographically incorrect, even though some sources do associate his birth with Blake Island more generally.

This sentence misstates the purpose of the March 1854 meeting.

Reliable histories of Isaac Stevens’s March 1854 trip say it was prompted by a murder investigation and armed response, not by a negotiation over Whidbey Island land ownership:

• HistoryLink explains that after William Young was killed, Seattle residents asked Governor Isaac Stevens for military action. Stevens then came north with soldiers, met with Chiefs Seattle and Patkanim, heard the account of Young’s killing, and proceeded to Holmes Harbor on Whidbey Island to demand the suspects.
• The U.S. National Archives likewise says that "two months later" (after Stevens’s January 1854 visit), Stevens rushed to the Seattle area "at the head of a detachment of troops in search of Indians who had murdered a settler." It describes the meeting with Seattle and Patkanim as part of that confrontation.

So Seattle’s involvement in March 1854 was tied to the aftermath of William Young’s killing and the search for those responsible, not to resolving a land-ownership dispute between Native people and settlers on Whidbey Island.