I actually ADD 1-1.5 tsp of sea salt to my spritzes and DCs. I've been doing it since 2009 with no ill effects. It makes my hair feel very soft and moisturized.
I agree with the ladies who have mentioned that it's such a brief amount of exposure that it might not be necessary to protect. Perhaps you can do two french braids using condish and a little oil. I don't know your hair type but my hair would be a poofy mess after being dipped in water. If you're going to dinner or something afterwards, the braids might help maintain a style.
Congratulations on your decision to be baptized!