We went on holiday at 10 months and had bought a cheaper umbrella style pushchair for travelling.
Defo second the sling suggestion, you normally give up the pushchair at the gate/airplane steps but don't always get it back until the baggage carousel so need to carry baby from plane, through immigration queues and then waiting around at carousel until it turns up - pack the sling in hand luggage and strap it on just before landing then can put baby in and carry easily until reach carousel.
We took the car seat but skipped the isofix and we got car seat and pushchair protective bags off Amazon - this meant could sneak some stuff in car seat like blankets, etc. I know people say to add nappies as well.
When you check in make sure to get a tag for both car seat and pushchair if taking, then car seat goes to oversize luggage so give yourself time to drop this off.
Security was fine, if you have a baby/pushchair they normally send you to a different section where you get pushchair scanned and also extra liquids - you're fine to take in excess of 100ml, I think technically it's reasonable amount for travel so we took 3 pre-sterilised 8oz bottles with cooled boiled water in (we were on nutramigen, handy for travel as is made up with normal temp water, but would have used ready made if could) and then powder in a formula dispenser. We got our bags drug tested as took a large amount of formula in hand luggage in formula dispensers to give leeway if checked luggage with the tins in went astray haha.
Do you know if the hotel supplies travel cots? Take your own sheets though as can be grotty and check reviews for them if you can, might be worth paying extra for additional infant items and taking own travel cot.
Not sure where you're at with weaning but we took a lot of CMPI friendly food, like fritters and muffins, with us to tide us over until could get ingredients to make more (we stayed somewhere with cooking facilities though). And defo take snacks! Especially to save yourself trying to google translate ingredient lists checking for milk products...
Also test the sun cream before you go, somewhere like arm/leg then face if that's okay, just in case allergy to it seeing as already allergy prone as milk allergy. We found Childs Farm fine, albeit a bit more expensive.
Sorry for the massive post! 