laptop keyboards are remarkably resilient, and usually work fine, once the liquid dries out fully.
The problem is often not the moisture itself, but the sugary residue it leaves behind.
My advice is to leave the machine switched off, and stick it in the airing cupboard for a day. Then review the situation. Laptop keyboards can usually be removed fairly easily, and if you search the web you might find there's a walk-through for your son's particular model. If you can remove the keyboard fascia you'll be able to clean around the contacts with glass cleaner on a cotton bud.
Otherwise, it's back to the makers for an overhaul, but be warned - this can be a pricey excercise.