The welcome dinner will take place on Sunday at 8pm.
The exact location of the restaurant will be known at the registration time
(Sunday at 7:00pm).
The restaurant will be at the short distance from the hotel Standford Terrace Inn.

Most likely: Il Fornaio

The price for the additional/accompanying persons will be known at registration time.
In general, prices of welcome dinners at IPS-USA conferences are about E100.