I can't think of a Judo throw that lands uke on the face, but watch out for the dudes with magic pants.
I would think that standing you will be fine I think they will have less ego to defend there, I think where its going to be interesting is on the ground where they all will want to prove themselves by getting the BJJ guy.
Enjoy it and realize that on the feet, you need to relax. If they get the throw, just take it. A weekend with Coach Josh helped that a TON. Don't be scared just take the throw and breakfall. They aren't trying to paste you. On the ground, expect things in general to be more based on pinning. Subs will have less set up usually and they will occasionally be surprised by sweeps you take for granted. Have fun and realize that there is a difference in the rulesets. Their game and your game have similarities but are not the same.
I agree with the oft said, "learn something from it." There are some Judo guys in my instructor's BJJ school and I try to do Judo with them as much as possible. Do I try to beat them? Not at Judo, I try to walk away with a deeper understanding of the standup game. Does it help me? A ton. I am also a blue belt in BJJ and the guys I "do Judo with" are all Judo brown belts. I occasionally get a throw on them, but they are letting me. I don't care about winning anything in class. Its class, not the Mundials!! Class/training time is about making yourself better. I only keep track of how I mess up, so I can try to not make the same mistake twice. With the Judo guys, I ask them how they set me up and what throw they used on me. Then they let me practise it on them. I do the same with them on groundwork.
Just relax, have fun, take the falls when standing. On the ground, be very conscious of your transitions. Once they've got a dominant position, they'll play heavy and your opportunity for a counter will be minimal. You have to catch them before this happens.
Many BJJ players play a little floatier, being more mobile and looking for a sub. With Judo, a pin wins so there is less of that. Salvaging a bad position against a good pinner can be much trickier than someone who's moving around exposing potential gaps during the transitions.
Thanks for all the advice, everyone! It was a great seminar, and I feel like I was able to pass on some knowledge to the judoka who showed up. As a warm up before sparring, we did one round starting from knees. I got paired up with a big tank of a judo black belt...he quite admirably tried one of the open guard sweeps that we had just drilled, but it didn't quite work. I was working a pass when he quickly sat up and accidentally headbutted me in the face. He made really solid contact right on the bridge of my nose, and blood was flying everywhere. I've had my fair share of bloody noses before, but this was a bad one! Took a good ten minutes before it had stopped and I was cleaned up. I ended up sitting out for the remainder of the time, not wanting to make any more of a mess than I already had. I still had a great time, though! Everyone was really nice and eager to learn. I feel like I made some new friends in the judo world, and the best part is that the club is quite close to my house, and as soon as I have time in my schedule I hope to start doing some training there.