I'm kind of an asshole -LONG

Marina❁ • 20 yrs.
SO I met this guy on Tinder, we hit it off great-- he's very sweet and nice. We go to  the same college and last Thursday we met up and grabbed some coffee together. We only hung out for about an hour...he's really nice but there were lots of awkward silences and the conversation kept dying down. And I'm not really attracted to him physically at all...if anything it's more of a mental connection because he's so nice but idk, sue me for wanting to be attracted to the guy I'm dating. 😅 The next day on Friday my best friend begged me to go with her on a double date with this guy she likes and one of his close friends. I reallyyyyyy didn't wanna go because I already had a date set for Sunday (tomorrow) with the Tinder guy and I'm not really one to date multiple guys at the same time. But she really likes this guy and she hasn't been on a date with him yet so I kinda took one for the team and went out with them.
(Side note, Thursday night when she told me all about this I texted Tinder guy and gave him a whole speech about how I had a date set for the next day and I'm only interested in him but I was only going for my friend and I would've felt bad if I went and didn't let him know, cause again, I'm not the type to date two or more guys at once...he thanked me for my honesty and that was that. Stupid I know..)
So I go on the double date and right off the bat I'm REALLY attracted to this guy. The only downside was that he was VERY quiet and barely talked to me at all, so I kinda took it as him not being interested in me-- come to find out as soon we all go home he's texting his friend and telling him he thinks I'm so nice and he feels dumb for being too nervous to talk to me. I told his friend to tell him that I'd like to have his number if it's okay with him, and I want to get to know him better without other people around. His friend sends me this screenshot later that night and I thought it was so so sweet..
My best friend told me she overheard him saying how he's really nervous and he can't believe I like him. We start texting, and he's so sweet and so so so nice. My issue now is, I have a date set with Tinder guy tomorrow. But I'm so much more interested in this other guy-- who I never anticipated to be interested in in the first place. It kinda just happened and I'm interested in seeing where things go with him...and I just feel like a big ol asshole now cause I feel too guilty to cancel on Tinder guy. Considering I hyped him up by saying it was just a pity double date...but I also wouldn't feel right talking to this second guy while out on a date with someone else.
If anything, I'm asking advice on how to let Tinder guy know I only see us as friends. If I do he'll know it's because something went down with the other guy at the double date. I haven't talked to Tinder guy much since it happened...I don't know ☹️ I'm thinking of waiting until after the date to let him know, so then it seems like I just didn't feel any sort of spark after hanging out together for so long..but I know how it feels to be in that position. To think everything's going so great and to get so excited about someone only to be told "I think we're better off as friends" and I'd really hate to do that to someone else....any advice would really be appreciated. 😕