What do you plan on studying at university? Violin? No one plays violin in our family, so I don't know about that. It takes hours of daily practice from what I've heard to become professional.
You are interested in instruments from completely different families. Most people on these boards play multiple instruments, but normally limited to woodwinds, or brass for example. When you practice a woodwind, for example, it helps you with your other woodwind instruents.
Let me present a different point of view.
Why not play trumpet if you like it? It doesn't cost much to rent one to try it out. My view is that different people learn in different ways and at different rates. I was/am a flute player. I tried alto sax in 10th grade, and I wasn't any good at it. I was a pretty good flute player. Why wasn't I good at sax? Probably because I wasn't motivated. I picked up guitar in college and added to my flute practice. I found it very easy and I learned it quickly. But I was motivated to play something i could sing with.
My daughter is 16 and now plays all the woodwinds. Adding new ones doesn't seem to detract from her main two, oboe and alto sax. This year her goal is to win some concerto competitions on oboe and sax. But she practices a LOT. And she doesn't listen to people who tell her she can't play more than one, nor does she learn a new instrument the way most people attempt to learn. I taught over 100 flute students during my years of teaching, and never had one learn the way my daughter did last night. The first five minutes, she learned the fingerings. Then she went straight to the Chaminade concerto, something she'd heard that she liked. Skipped all the Rubank books and scales. Three hours later, she could play it. It will take her a while to get a really clear sound, but it's not going to take her long. She says the flute is easy, and I guess it is compared to the other woodwinds. Why didn't she learn the flute a year ago when her sax teacher showed her how to play it? Because she wasn't motivated. For some reason, last night she was.
As far as dividing her time, she generally alternates days practicing sax or oboe, several hours each day. But she's been playing both for over 6 years, so she has a solid embouchure and playing style. She added clarinet about two years ago. Her motivation then was to be able to play in pit orchestras for musicals. So she learned the clarinet in about two months. When she practices clarinet, it helps her sax playing so she can do that less. Then she studied the bassoon seriously shortly afterwards. She doesn't practice that much now, but seems to be able to pick it up quite well with a half hour practice. I think the oboe embouchure makes it much easier for her to do that than for someone who doesn't play oboe. When she has a musical coming up, she'll practice the clarinet a lot, but in between she'll let it go for weeks. Her sax teacher says her regular soprano sax playing allows her to play the clarinet well. She tries to get to her other instruments once every week or so ( baritone sax, English horn, bassoon, Eb clarinet, and now piccolo). If she wasn't a full-time high school student, she'd practice them more.
People who play trumpet can give you better advice, but my guess is that you would have to play it regularly to play it well, because you don't have another way to keep up your embouchure. But are you trying to become a professional trumpet player, or do you just want to be able to play it? If more for fun, why not just try it? There are people on this board who play all kinds of combinations of woodwind, brass, string and more. They must be able to maintain them somehow. What I see with my daughter is that she practices her "extras" when she's tired of playing her main instruments. She uses time that she wouldn't have used anyway to practice her main ones, so she isn't taking away practice time by learning new instruments.
