LOL is fine if it's literally meant as a laugh out loud at something hilarious.
Otherwise it's utterly ridiculous. I got a text from a friend recently; she'd sent one text inviting us round for dinner soon, she then sent a second text saying something along the lines of "we're inviting Anne & Simon too lol". What's so funny about that?! (For background I might add that this friend, like us, is middle-aged!)