Congrats on making your first overseas flight (from I assume LAX to FCO) a nonstop one. I am in the camp that whenever possible I prefer to reduce the number of flights/takeoffs/touchdowns/airports on my journey to Europe. To help me be as comfortable as possible onboard and have the best chance to accumulate at least some sleep during, I opt for an appropriate travel wardrobe (but no, I do not wear pjs; think forgiving fabrics/waistbands/slip on shoes/nothing restrictive or complicated) and have with me a well curated personal bag with all of what I consider necessary: back-up travel paperwork (I use the airline's app for tickets/itinerary, have accommodation info/site reservations on my phone) entertainment digital and otherwise, food, OTC sleep aid -- I like/have success with TylenolPM or equivalent, spare undies, toiletry bag and disinfectant wipes. Giving a fresh swipe with a cleaning wipe on chair back, arm rests, tray table gives me peace of mind and starts my settling in process. During the flight I push my water intake (needing to use the facilities is good for stretching stiff body parts) and avoid sugar and caffeine. Sometimes I travel with a small pillow or will utilize a sweater or pashmina type scarf for support and/or warmth. I use my own earbud headphones and have not used an eye mask though I know some people need the complete darkness for any sleep to come. I lower my expectations for good, restful or plentiful sleep and gladly take the short snoozes if that is how they happen when I'm up in the air. Upon arrival I choose to stay up and moving, try to eat a meal timed when the locals would take a meal, and make going to bed as late as I can. I won't have an early morning start activity planned for my first full day, preferring a leisurely awakening/getting ready/having breakfast. I can imagine, planning on what works best for your youngster will be critical and packing along patience and a slow and steady wins the race attitude probably helps a great deal. Have a great trip!!