Flirting

Would it be weird if I messaged a guy this?

So while on vacation, my sister, her boyfriend, my mom, and I met this very nice German man who lives in Japan (that’s where we are on vacation) and was on a trip with his mom. My mom invited them to do sparklers with us (the fireworks where you hold it and light the end) and they agreed to. We ended up all chatting for a few hours and after my sister and her boyfriend went inside, he asked me for my Instagram so we could stay in touch when I said that he should hit us up if he’s ever in the states and wants to come to Washington. Anyways, it’s been about a week or two and I haven’t heard from him aside from us following each other on Instagram. I’ve been thinking of messaging him something like “hey! I just wanted to let you know that I think you’re super nice and seem pretty cool” (not the exact wording I’d use and I am open to suggestions on better wording) but would that be too weird? Keep in mind he’s five years older then me.

Updates
+1 y
He posted a cute video with a cat so I slid and said “aww! So cute!” and he didn’t say anything back, just liked the message. Does mean something or no?
Would it be weird if I messaged a guy this?
Post Opinion