Took our dd on a skiing holiday (family wedding) when she was 15 weeks. Took a pack of nappies, but distributed them around the case - it had a zipped lining between the outer and inner, so filled it up - felt like a drug nappy runner! I bought more nappies there. Bought a couple of cartons of milk at Boots for on the plane, just in case. I had also done a bottle and had to taste it for customs!
I was mainly breast feeding, with a little forumula, to top up before bed, so took that, with one of those measuring containers with lids. I took a small plastic ice cream tub and sterilising tablets, so filled that with water and kept a spare bottle/teats in, rinsing before I used them in the bathroom. I needed a kettle, which the hotel supplied.
Apart from my usual nappy bag, it was easy, she wasn't moving around, was happy to be snuggled in a pushchair. I even got to ski, although it was tough on my boobs!
Went again 8 weeks later and was just starting her on solids, took some dehydrated rice and got a couple of purées there. Again, bought nappies, they are much the same and it is interesting looking around the supermarkets! (I'm sad!)