Liquid can't be taken through security, meaning the personal and hand baggage check, but I have never been in an airport where water and other drinks where not freely available beyond security, nor on a plane where there was not drinking water etc available. I have never seen anybody stopped from taking beverages onto a flight. If you have your own water bottle take it empty, and use a little old bottle for water that you don't mind dumping at security.
The worst thing about airtravel and especially international travel is the standing in line and very often the considerable distances you often have to walk. They often don't know what gate the plane will be leaving from so you might not know how long you have to walk to the gate. Standing in line at check in, security, and immigration the waits can be very lengthy especially on arrival. I strongly suggest asking for assisted (wheelchair) travel . You do not have to be physically disabled - they dont even ask you for a reason but they do ask if you can walk at all so they can assess the amount of help you will help. I usually offer arthritis as a reason though when I am asked that question saying it is the distances and the standing that are so hard for me. The advantages are - priority priority priority, at check in, going through security, customs, immigration, help getting baggage off carousel and first on ( but last off) the plane. Cabin staff will help settle you and put hand baggage in the overhead locker. You can visit duty free and will be helped to make your selection by a sales person This service is available even if you have a fit travelling companion.
Internal travel in USA and changes in Europe can be very physically demanding too. It seems a rule that if there is a transfer involved the departure gates will be at the furthest possible distance from each other, even if they are the same terminal. The only time I have been badly let down with assistance was at O' Hare Chicago. They hadn't ordered the chair and service was appallingly rude. My plane had been late departing so I was short on time to catch the connection. I only just got it but I realised that if I had tried to walk it I would probably have missed it. The assistant took short cuts. Tip: if the cabin staff seem to have forgotten you, remind them at some point so they can call through to make sure it is organised upon arrival.