You're based at the Holiday Inn By the Bay Friday through Monday, which puts the whole peninsula inside a fifteen-minute walk and the whole harbor inside a half-hour ride. The hotel's e-bikes are free — that quietly changes what's reachable, so there's a full route section below. Everything the hosts specifically called out is badged host pick.
The hotel lends e-bikes free to guests, checked out at the front desk and subject to availability — so ask on arrival and again the night before rather than assuming three are free at 9am on an August Sunday. Portland is small, hilly exactly where you don't want it, and ringed by flat waterfront trail: a near-perfect e-bike city. All routes start and end at 88 Spring St.