April 9 is Internet of Things Day.
I selected Cafe Regatta finally as the venue. Its is by the sea side and in general nice place if the weather is fine. No reservations possible there but lots of free tables outside and a relaxed athosphere.
If you are new to Helsinki, Sibelius monument is nearby, you can walk past it on your way if you pick the right bus stop (assuming you came with bus...)
also next to Töölö rowing stadium if that type of things float your boat
As panic plan if the weather turns really nasty on the day, we can try to seek refuge at nearby restaurants (like mestaritalli) but this just if we have a what we finns call 'normipäivä' (jour de la normal).