I'm a normal kid in band. I have played Bass Clarinet since 7th grade and i have marched the Bb Clarinet for the past two years. But I have had the worst time switching back and forth between the embouchures every day that I am considering switching for the next two years. My band has a need for Mellophone players, and good ones at that. Is the switch difficult and/or worth it?

Wow, I had to look that up because I'd never heard of it!
Your embouchure for bass and soprano Bb shouldn't be that different. Bigger and slightly looser for the bass, of course, but it really shouldn't be too hard to go between the two - I would suggest talking to a teacher who is experienced with both instruments, and ask them to check that you have the embouchure right. It might be that you just need a bit of tweaking and it'll be much more comfortable.
I'm going to start trumpet soon (if I can find a decent one on a small budget!) but from what I've heard it'll take you a while to get to grips with brass, unless you've played before. Yes, you already have the note-reading and musicality sorted, but the embouchure is really very different, and it'll be a while before you can play well enough to do it in your band. I would suggest sticking with the clarinet, asking a teacher to help you out for a bit, and if you need to, drop either bass or soprano, and just play the one you're most comfortable with.
Otherwise you could start learning mellophone now, and carry on playign clarient in band for a while - then switch when you can play well enough.

Most people get used to switching after a time. It can be a useful thing to do as in many areas, like playing in musicals, the ability to double is essential. Personally I have no problem switching from bari sax to bassoon - a much greater change than bass to soprano clarinets.

Good luck