I quite enjoyed travelling with my dc, and at those ages you can see a city in a completely different way than you will as adult tourists.
We divide our day into a morning outing and an evening outing, and return to our base in the afternoon for a siesta. Only ever try to do one thing, always buy the tickets advance online to avoid queues and research your city so you know where the playgrounds and parks are.
I vastly prefer self catering over AI with dc. Simple breakfast in the apartment, picnic lunch, and dinner on a timeline that suits the dc. It doesn’t stop you eating out but it gives you flexibility.
For airports: Get your dc to carry their own bag - not too heavy obviously but a little bit of weight in a back pack is very calming and also makes them feel important. iPads are a godsend.
We always followed a pattern when travelling that dad led the way, and the dc followed him in age order with me bringing up the rear. It saved endless sibling arguments, and we never mislaid a child. It also meant that going through a security barrier there was one dp either side.
Practice the security check as a role play game before flying. And look up the rules yourself if you’re not sure. Many airport websites have information for autistic children, with photos and clear explanations - and it’s great for showing all kids (and adults) what’s expected.
Buy a cheap umbrella fold stroller for the trip. Don’t leave an expensive travel system to the mercies of baggage handlers. And an umbrella fold will give you better flexibility on the go anyway. Pack light. Assume that at some point you’ll be carrying all the bags and the children.
Bring lollipops for the airplane ear pressure. And don’t pass a toilet without a visit.
once you get going, travel with dc can be really fun- but you have to manage your own expectations as an adult. If you get the right mindset it can be brilliant. You tend to meet locals, rather than tourists, and sometimes see famous attractions in a different way (the cats at the colosseum and the pigeons at the Eiffel Tower stand out in my memory). And it is magical to see places through a child’s eyes. But that means being willing to go at their pace.