I get it. It is new, age doesn't stop us from worrying about our children, I'm currently worried about my 30year old although I would not dream of letting anyone irl know.
Plus covid had stopped so many rites of passage, many still seem younger than 19.
Bank accounts. Starling or Monzo don't have fees. Since covid some places prefer card and the difference paying on card compared to cash is negligible. Make sure he does have some cash, there will also be a tourist tax to pay, get him to find out how much.
Talk to him honestly about drinking and the importance of eating, give him tips, drinking lager as suggested is a good one, but tell him to look out for the ABV% on any alcohol he drinks. Knowing how strong and making different choices helps, I still do it now, I choose the lowest % wine. He might not drink much anyway.
Talk to him about the dangers of water and alcohol, if he doesn't live near the sea in the UK Talk to him about general water dangers, the RNLI have some great resources.
Get him to check his phone contract and see what the charges are, sometimes you can buy a bolt on travel add on for one month.
Finally, you can't expect him to give you updates, be contactable to a schedule. He needs to spread his wings, does he use SM as this can be a way of seeing he is OK (every Insta using teen that I know has a page for everyone and a page where only friends can see, so it is sanitised information)
Has he got the EHCR card (or whatever it is called now E111 to old people) help him book his travel insurance, make sure it is a 5 star policy and includes repatriation.
Take a photo of his passport and make sure you and him have a copy, if it gets lost it is easier having all the details. Fill in the emergency details on the passport. Have the hotel details at home.
And be proud, you don't want him in his room for the rest of his life.