Yes very walkable without mobility limitations. A major reason however, to go to the Sitka Heritage Park is for the 1 mile loop trail past the totems and fort site. Purchase the cheap guidebook, really enhances the walk. Then from there the Raptor is uphill a 10 min. walk. There is an all day shuttle $7 last year, that also goes to these locations. Be sure to also request the Sitka visitor guide. The dock is "downtown". This is a tender port.
For clairfication- safe- is a true word in Alaska, on the Inside Passage ports, completely safe.