We are expats living here in Chicago. We travel to Europe all the time (UK annually, France and Spain last couple of years, and France again this summer). We will have a 3yo and 5mo old in the next trip. It’s def doable and completely safe! I’d say the only part I dread is the red-eye and associated jetlag because it’s very hard to sleep as an adult when you have a child to stop falling off the seat/keep buckled in when there’s turbulence etc etc). But I find going there easier than the return because when you get there everyone just stays up late and that’s fun. Coming back is excruciating with little ones though because everyone is waking up at 2am/3am etc and it takes us a good 1-2 weeks to get back to normal. But your 10 year old will probably be much easier with it than my toddler who can’t understand time zones yet. As for practicalities, there’s really no difference to car hire/hotels etc than language barriers, and the experience of other cultures for your 10 year old is so worth the extra effort in terms of logistics. Further to @
anette’s comment on diapers, it’s worth taking enough for a day or two but scope out where the nearest hyper market (Carrefour is the big one) is and just go there to get supplies. It has all the major brands like pampers etc (just know how to convert to kg for sizing). Baby food pouches are less of a thing, however, but you can get some there too. If you pump milk still then just be aware that your pump might need a dif adapter to run (UK voltage is 240V, I think Europe is 210!? ) Otherwise tap water is totally safe in MOST places in Spain. The coffee is amazing, so is the bread, pastries, the food is out of this world. ahhhhhhhhh I miss Europe