ü - u umlaut - is NOT pronounced like u in English. It's "y", not "eye", not American y, but European y, like "u" in French.ö - is NOT pronounced like o in English. It's like "eu" in French. Like "i" in "sir" or "bird".
Glühwein is better to pronounce like "glue-wine" and glögg like clerk or dirk but without the "r". Try saying "glerck" and then drop the r. Nevertheless, even with the r, glerck is better than clog.
How ever you pronounce it, have a "glöggfest" next weekend or weekend after that.
(It might be best to call it "mulled wine" :-D Because that's what it really is.)
The form is more like a cocktail party, except that people are dressed for cold autumn-winter days, and behave like on a nice family evening. Loungewear is the proper dress code, and fleece and sweatpants are fully acceptable outfit. I mean... we are speaking about Scandinavia. It's like Europe's Canada.
(Just google "glöggfest" and look at what people are wearing.)
Because of the free form, glöggfests are very casual and friendly events.
The appropriate time is the evening, after 6 but before 10.
There is specific glögg crockery
Now, if you can't get a hold of one of these, any cups are fine. Coffeecups are better than teacups, though :-D (Or you could use the small, cylindrical ceramic sake cups.)
There are not many varieties, usually only one, perhaps two. Often the #2 variety is alcohol-free, but sometimes it's just different kind of glögg, like one red wine glögg and one white wine glögg. It might be better if you see that there is an alcohol-free variant, especially if you plan to allow kids to be with you, and something nice to drink for people who don't like mulled wine or warm cider, like coffee, tea or hot chocolate. Now, as it is Samhain, it might be more fun to serve something more Samhain-y than mulled wine, like mulled cider or hot pumpkin cider.
See that you have at least two cups / half-a-liter / a pint for each guest, that would give them 2-3 little cups of glögg, and other drinkables, like water and coffee.
As food, you should have gingerbread and other spicy cookies, cakes and pastries and - if you want to do like the Swedes, you'll serve the Swedish saffron buns. Gingerbread is really good with blue cheese. I like to serve also small savory pastries, hand pies and pirogs. Liver paté is good with mulled wine, I can imagine it's ok with mulled cider as well. Dark bread is better than light bread, like Danish rye, Russian rye or German pumpernickel. You could try the Steakhouse bread, with cocoa. Then different cocktail snacks, like spiced nuts and so on, are very good too.
See that there's about 6 pieces for every guest, and have a little more than that.
You can also arrange this as a holiday special for children. I think, for children, it would be better to build it as tea party, with hot cocoa or apple juice or something else nice, in stead of tea. In my mind tea parties are all pink and girly, but this one would be more what Wednesday Addams would do with her friends, if she had any. :-)
I think this looks like a lovely kids' tea party with hot pumpkin cider.
Now, if you are planning on having a "mixed" guest list - kids and adults - it might be a good idea to see that you have a couple fun family Halloween movies ready for the children to entertain themselves with, because adults can be really boring, especially when they get a little alcohol in themselves, and there's plenty of good food and good company. And teenagers might prefer to pretend to watch the "stupid kids' movie" when they actually are watching each other.
For a cocktail party it's a good idea to see that there are too few seats, so that people mingle, but this is a glöggfest, so see that everyone has a seat by the table, either kitchen table or coffee table. This is very informal party, mind you, and it's supposed to create the "having a sibling/best friend at visit" air. So don't invite people whom you are not that good a friend with, or people you don't know, unless they come with someone you know very well. Of course, this might be a good time to learn to know people, but it's more fun with just "your girls".
Also, you need to see that your guests get home safe and sound. Some people react worse on the little alcohol there is in glögg, and might need help to get home. Having an adult PJ-party and sleepover with your friends might be a good idea, and then you can see that there is a nice breakfast, easily prepared, like froze in some breakfast casseroles.
It's also a good idea to end a cleaning bee with a glögg fest, to thank all who came to help you with cleaning.