Take sterilising tablets.... you just need to fill sink up, pop in a tablet and your pump/bottles for 20min then air dry,
Do you really want the hassle of pumping on holiday though. Breastfeeding is so easy and in hot weather it will be very often so finding the time to pump will be few.
At 3 months I’d imagine your baby would be too young for a stroller, unless it’s one that lays fairly flat and can keep him/her in safely. If it’s going to be very hot, might not be suitable to baby carry... but you can get some that are recommended for warmer climates too.
Can you hire a car seat there? Just thinking about less hassle for you.
No advice on breast pads, luckily by 3 months I’d stopped leaking. You could perhaps look into those bamboo reusable ones? Less conspicuous IMO.
You can get newborn sun protection - I think boots might do it but I got mine from amazon (think baby). Hats with big flaps, eye shades annoyed my baby, thin legged rompers are probably best for shade and keeping cool, umbrella for pram for shade, tent if your by pool/beach, sponge mat from supermarkets for bath (stops them sliding and super easy to pack), breastfeed on take off and landing and baby will be fine, definitely take a meds supply.