LDS weddings differ significantly from non LDS ones
It will depend a lot on how your children want to go about it. In the church it is perfectly acceptable to be sealed at a temple (free) with pictures taken by the local laurel for 50 dollars, and then have a reception later in the day with a bunch of Macey’s popcorn on a basketball court with Sister Smith’s tablecloths while people chat and shake hands in a line with the bride and groom. You could throw an entire wedding for less than 200 dollars. (This also wouldn’t be really a wedding for people outside the church).
Costs add up for what you want to do and how much to entertain. The biggest expenses will be venue, food, photos, and flowers (and drinks if alcohol is desired). Do what works best for you, but I would advise spending good money on a photographer and photos. That’s not an area to skimp.