Traveling can be hard for picky eaters since your thrown head first out of your comfort zone . So your likely going to Barcelona and either got kids that are picky eaters . You arrive in Barcelona from either your long or short flight.
You come to Barcelona not to just eat Mcdonalds but to eat the local cuisine so just learn what food is common in Spain and maybe go to a Spanish restaurant and try it . If you don`t like seafood avoid seafood paella maybe go for the meat of veg option . Not my fave but decent the taste stays in your mouth.
I`m sure you like dessert maybe try the chocolate churros – which are lovely .

la boqueria , a popular market in Barcelona you can find many fruits and vegetables which make the market shine through the hustle and bustle of the city . A heaven for foodies but can be very busy so make sure your early! if your a picnic type of person you can find tapas restaurants serving baby squid on egg – which seems gross . Jamon or ham in English is here seeing it hung up you can get some of it you can get ham cones with cheese .
Just to warn you the smell can make you feel sick .
Central hamburger
So you might be sick of Spanish food but relax this is a good one . They have menus in English and the burgers are really good and I even went here twice
https://www.lacentralburger.es

So there are many restaurants and cafes that serve chips hot dogs and pizza
Don’t let your picky eating ruin your travels
You can find ice lollies in La Boqueria. Relax I know sure you will find something to eat there are many Italian and Chinese restaurants and I have found many restaurants serve Patatas Fritas - Chips (Fries) . Also Patatas Bravas also a potato based dish.
Happy Travels – Em 🙂