well since you're asking internet strangers about how your parents will react, i'll go ahead and pick apart your post more aggressively to emulate their response more accurately (keep in mind i do get it though, i had a much, MUCH longer ldr than yours get very VERY serious much MUCH quicker). so heres how they're going to react

you've been dating for four months and consider it serious but consider seeing each other on a regular basis "every month or so"? so how many times have you actually met up? not to mention how you met to begin with. which, if i'm reading correctly, you don't address in this post, so i'd advise you to find a plausible explanation other than the internet or tinder before this happens if your parents are as conservative about ldrs as you insinuate.

I've talked to my SO about it and a few other friends but have gotten different responses and we're all around the same age

my final point is about this 'cause i did giggle when i read it. plenty of people had completely healthy relationships with this kind of gap at your age. but i need you to know, and you'll know when YOU'RE 24, whether you're still with this guy or not, you are really not the same age. not at all. whatsoever. and your parents will absolutely pick at that too and you need to be prepared for it and it's so better that you come to terms with that very valid reaction now, not only before they meet him, but just in general for your own sake