St Matthew's Church in Worthing, West Sussex, will host the service at 6pm on Friday after Becky Dobson, 27, her boyfriend Stuart Hill, 30, and his brother Jason Hill, 32, died.
Prayers will also be said for survivors Ellie Milward, 29, Jonathan Udall, 32, and Jennifer Barham, 39, who are being treated for critical injuries, and pilot Scott Booth, 42, who was also injured.
Vet receptionist Ms Dobson had been celebrating car salesman Stuart Hill's birthday with him and his brother who is a lawyer.
The Rev David Hill and his wife Sandra, who attend the church, described their sons as "remarkable people". Mr Hill is also a Baptist minister on its preaching team.
Ms Dobson's family will also be present at the service. Her father Peter said his daughter, who had ambitions of becoming a veterinary nurse, was "full of life" and "always happy".
The Airbus EC130 B4 crashed just before sunset on Saturday on tribal land in a section of the Grand Canyon outside of the national park where air tours are not as highly regulated.
The three, who are originally from Worthing, died from multiple injuries in the accident, Mohave County Medical Examiner's Office said.
The preliminary findings were released ahead of full post-mortem examination reports which could take up to six weeks.
The cause of the crash is being investigated by the National Transportation Safety Board.
Investigators will interview witnesses, survivors, the helicopter operator and manufacturer and others before issuing a full report in at least a year's time. Preliminary findings are expected before the end of the month.
More than £14,000 has been raised for Mr Udall and Ms Milward who were on their honeymoon at the time, according to a JustGiving crowdfunding webpage.
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