You are playing the King's Gambit. You must have no fear, and will show your opponents time pressure is not alleviated just because this is classical chess instead of blitz! ahem Uh, Anyways, on a more rational note... just know, under ~2000 (I won't speak above, since my highest OTB opponent of admittedly few total games was mid-1900s USCF at the time) even if they have a set response to the opening, whether it's the Falkbeer, Fischer, or Schallop, what have you, you should know more about the opening then they do. Part of what's unappealing in the KG is the amount of understanding necessary in radically different lines just on the off-chance they don't play the French, or the Sicilian, or the Caro-Kann, etc. On the flip-side, it's actually what I do find appealing to the King's Gambit. I enjoy being able to set this game as "different" from the Sicilian matches I'll likely play for the next 3 rounds straight (since I play it exclusively on the Black side against 1. e4 it's not an unlikely scenario for me).

However, you're basically giving up the control of flow and offering Black to find a solution for themselves. From what I've seen, personally, up until ~1400, it's fairly easy to tell your opponent is likely out of their comfort zone from the get-go, and up until ~1700s, while they do know of the opening and have a general idea of the first few moves, the game is likely to end up a miniature regardless. Once I started playing a couple 1900+ players the games felt... restricted seems like the best way to put it. There are responses for every type of player for Black, and once I hit opponents of this caliber, I realized how little I actually "knew" of the KG. I took a slight blow to my commitment to the KG when I got stomped by some makeshift Fischer/Hanstein hybrid with a queen-side castle. It's also when I learned that part of knowing the King's Gambit is being able to turn that slight edge into a winning endgame (especially the queen-side majority endgames), not some 8 move tactical trick.

TL;DR: You're not fighting for the champion title, your opponents have likely not scoped you out and prepared hardcore against you in particular, and above all, these games are going to be enjoyable for you (I can't promise the same for your opponent). Go for it.