At 2 years I would say some if these things not needed:
Pram - will you actually use? Mine never used a pram at 2 in uk so def not abroad, but even if you do most paths are bad for buggies in Spain as narrow/ not well maintained, buggies don't work on beaches, and hotels often have Los if steps in and around restaurants/ pools etc. airports rarely gt pram back until exit with suitcase anyway so still have to walk at airport.
Reusable swim nappies - have you considered toilet training? Even if not perfect before you leave they can be trained enough to not need swim nappies and to poo in toilet so you don't end up with pooey nappies needing changing on plane/ in taxi etc as can use toilet and just nappy for wee if needed
On a plane please don't take playdough! It's always mentioned on here but it would be very annoying if next passenger sat on seat with bits of playdough hidden in sides.
We take very little tbh on plane. If it doesn't fit in handbag/ rucksack by feet it's too much as you don't want to be getting up and down every 5 mins to open storage above, plus you can't during turbulence or when seatbelt sign on
We take:
Spare Tshirt, pants, leggings for kids ( folds tiny)
Spare pants, and Tshirt adults
Travel wipes
Lip balm
( all above folded into small wash bag with zip)
Empty water bottle to fill after security
Few snacks ( cereal bar, nuts)
Phone charger ( need now with new security on electronics)
Ipad
X2 tiny books
X2 tiny notebooks and pencils ( x2 children)
Might sound limited but this has honestly worked great. Have now 3 and 4 year old. Travel approx x2 times a months since birth.
Small baby add sling and a nappy for every flying hour plus 4 spare. So 2 hr flight, I would take 6 nappies. 10 hr flight take 14 nappies.