updated 07/01/2013 AT 1:00 PM ET
•originally published 07/01/2013 AT 5:25 PM ET
In town for their son Samuel’s baptism, which took place at Garner’s family’s parish, Christ Church United Methodist, on Sunday, the pair also celebrated their eighth wedding anniversary on Saturday night.
Affleck, 40, Garner, 41, and their daughters – Violet, 7½, and Seraphina, 4 – joined Garner’s parents and her sister at an 11 a.m. service, where 16-month-old Samuel was baptized.
“He’s really cute. He was wearing little blue overalls,” a parishioner tells PEOPLE. “He kept trying to high-five the pastor as he was getting baptized.”
As for Samuel’s sisters, “Violet was very well-behaved,” the parishioner says, while “Seraphina was funny – she was running around, and Ben had to keep getting up to run after [her].”
Dressed in their Sunday best – Affleck in a fitted suit, Garner in a white dress – “they looked really happy,” the source adds.
They were in equally good spirits the night before at local pizza joint Pies & Pints, where the couple celebrated their anniversary with a low-key dinner of beer, pizza, salad – and a side of PDA.