Well, yeah.

How many outputs does your laptop have? Only the headphone output?

There are laptops that have 3 stereo outputs (3x2 = 6 out).

So, in those six channels, you've got
left/right front
left/right rear
sub
center

.....

You can use the splitter, but how many outputs does it have? It wouldn't be good to be splitting the subwoofer's feed.

BTW: From what I understand, you're DJing this party... and you're buying the speakers now... ok... if you ain't a DJ, and you're buying speakers only for this situation, place the speakers on a HIGH level, pointing semi-down... because if you place them at people-level, you're going to have to UP the volume so much, you'll blow them.

Unless you buy some heavy duty equipment... like some Peavys or something.

Wow.... memories from my DJ days...
I built this super-mega-moFUCKER speakers... I used 3 amplifiers per speaker... 6 amps total. Two amps where 600Watters. Two where 550. Two where 1000.

My parties thumped.