breastfed baby taking formula for one day.

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My 5 week baby is exclusively breastfed ( breast and bottle- I had a really sore nipple) and has been since birth. In a week and a half my best friend is getting married and I am the maid of honour. It will be a very busy day and I'm starting to feel stressed about how I will feed my baby. I was hoping at this point I would have breast milk stored to give him the day of the wedding but right now I'm only a bottle ahead of a feeding. It was suggested to me that I give him formula for the day (especially since it's likely he could be going through his 6 week growth spurt-- the 3 week one was hell) to keep him fed and satisfied and to allow me to enjoy my friends special day. My question is, has anyone ever given their 6 week old baby formula for just one day? How did it go? Do you have any tips or advice? I will probably try the formula a few days before the wedding to see how my son reacts to it. Also what kind/brand of formula do you suggest I use?? Thanks