HELP

Will you have access to a washing machine or a store while you're gone?
Breast or bottle feeding, or combo? & do you know roughly how many diapers baby typically goes through in a day?
I personally prefer to be over-prepared rather than under. When going somewhere I won't have a washer, I typically pack at least two outfits per day; babies are messy at the worst times, and their clothes are tiny enough that they don't take up *too* much space, especially summer outfits.
If you have access to a store that would have the diapers & wipes you use, you'd probably be safe to just pack a few more than you think you'd need. If you won't, and you have the space, I'd bring an extra pack (like the smaller packs in plastic).

I would start with asking yourself “How many diapers does my 3 month old use per day?” And then multiply that by the amount of days you’ll be gone and add 10 more for good measure. Then a pack or two of wipes. If bottle feeding then bring the bottles you’ll need, if breastfeeding and pumping, then don’t forget the pump and accessories. But if you’re JUST breastfeeding, then only the items needed for that (like if you use nipple cream, a breastfeeding cover, pillow). I would suggest 5 PJs, and 5 summer outfits (if you’ll have access to a washing machine). Otherwise, then pack 8-10 PJs and 10-12 daytime summer outfits. If your baby sleeps in a crib, you might need a pack n’ play unless the place you’re going to has one. If your baby sleeps with white noise on, probably the white noise machine. Then travel size hygiene stuff for the baby (shampoo, baby wash, lotion, sun screen, etc.). Don’t forget the diaper bag and if you baby wear, the baby carrier. If you’ll be driving, the car seat.