As soon as you can! Narragansett is a beach town and places book up fast for the summer. Check the "Lodging" page for hotel blocks and suggestions.
We love your children, but due to space constraints our wedding is an adults-only affair. We hope you'll take this opportunity for a date night or couples vacation.
Providence (TF Green International) is closest; it's a 25 minute drive from the wedding venue. Boston provides more flight options; it's a 1.5-2 hr drive from the venue depending on traffic.
We'd recommend renting a car. There are rideshares in the area that can work in a pinch, but be aware that they tend to be slower and less reliable than you'd find in a bigger city.
The closest train station is the Kingston Amtrak station in South Kingstown (not a typo, the station is Kingston, the town is South Kingstown), about 15 minutes from the wedding venue(s).
South Ferry Church: There's a parking lot, and overflow parking is available across the street at the University of Rhode Island Bay Campus, about a 5 minute walk away. The Towers: There's street parking along the sea wall and on nearby local roads; if it's a beautiful day, you might need to walk a few blocks.