I have a question I was hoping you guys might be able to help me with. I am throwing a big surprise graduation party for my husband who is getting his doctorate this spring. In addition to inviting friends and family I also invited coworkers of his from all of his past jobs, and his present job. About 45 coworkers were invited. In all I am expecting about 100 people. I did not include significant others of the coworkers, unless he was friends with both people. I did this mainly because the function hall can't accommodate many more people (120 limit). Plus, it is costing me $30 per person, and if the 45 coworkers turned into 90 coworkers I couldn't afford it! Was that rude of me?
Coworkers are now beginning to ask if they can bring guests. I'm afraid if I say "No" to the people who ask, they won't bring guests. I know there will be some people there who won't ask but will still bring guests and that wouldn't be fair to the people who asked. Plus, I hate to just say "No." Or should I tell people that I would need to wait and see how many people RSVP because we are almost at the room limit? But that seems awkward and complicated.
Not sure what to do. Any suggestions?
You defined the parameters of the party, and the purpose. Excluding partners of former co-workers is not rude in the least. Why would you invite them? Regardless of the argument that this is a social event, it's still centered around the professional aspect of earning the doctorate.
So no, you were not wrong to define the parameters of your party.
Those who received clearly worded invitations are wrong to call and ask if they can bring someone. The invitation tells the recipient who is invited.
If there are those who (rather oddly in my opinion) "would NEVER attend a party" without their partner, then good.

That relieves you from having to pay for that person.
I would NEVER WANT to attend a function that had anything to do with my wife's work colleagues and relationships. That would bore me to tears. I don't know those people, and don't necessarily care to spend my very limited free time with them. Also, she would then feel constrained to "stick by me" as I wouldn't know anyone, and that would interfere in her ability to renew acquaintances or network.
So. Go ahead, have the party, tell those impolite enough to ask if they can bring an uninvited guest that you are too concerned about the size of the reception accommodations and go with it.
Honoring your husband is the key here, eh?
An aside: My siblings and I hosted a 25th anniversary party for my parents. Their dearest friends were out of town (state actually) and would not be able to attend. So, my sister in charge of the invitation sending did not send them an invitation. They of course, returned unexpectedly and were really offended that they didn't get an invitation. She explained her "reasoning" saying that she didn't want to pressure them... whatever. They were upset.
They got over it. So did we. They remained friends with my parents.
Things happen, ya' know? Move on.