This is the safest way to greet a pair of people. Refer to them together and neither one gets preference.
Lads, though, you gotta be careful with lads. Here, in the hills, lads pretty much just means boys. Like, actual boys, like kids. So a greeting like this could either be condescending or affectionately familiar.
In the UK, lads have their own culture. Lad has found its way into an adjective, showing many men to be laddish – which, sure, could mean boyish but not in the red cheeked, child-like way. We might call a lad a frat boy here in the States, also a word that would suggest childishness but tends to refer to a rather boorish behavior. Lads drink too much and make too much noise at the game. They travel in packs and tend to not be terribly respectful of women.
But you know – people use both boys and lads to show affection to a group of men. My grandfather went out once a week with the Boys – even once they became the Romeos (Retired Old Men Eating Out.) I think Englishmen hang out with the lads down at the retirement home but I’ve never heard an American man talking about the lads. In fact, I’m not sure I’ve ever heard an American use the word lad without some affectation – without pretending to be posh or English or some combination of the two.
A case could be made for Rosencrantz and Guildenstern being any variety of lads.