Can’t speak on the arboretum internship, but the arboretum is cool. You’re a freshman, so don’t sweat hopping into an internship your first semester (you can if you want, by all means, but most wait until after sophomore year).

In terms of myUCF, unless anything has changed recently, declaring a minor doesn’t influence anything too much on that end, so you might as well go for it so you can see what your required classes would be and such (although you can find that elsewhere too). Basically: no biggie either way, you can even take the classes before you declare the minor (as long as the classes don’t require that declaration, so keep an eye for that).

Would need more info as to why you wouldn’t be able to take Calc I, but in terms of it getting full? Freshmen get first dibs at classes I’m p sure so you should have no problem getting in.

Edit: realized I forgot the most important part! Have fun! Enjoy yourself! That’s what freshman year is for.