For many reasons (some of which I'm sure you can guess), I only had a dozen guests at my wedding. For those of you who may also be having tiny microweddings (or even eloping) here's my advice for how to talk to guests who weren't invited (who may be dealing with hurt feelings).
When talking to the not-invited, DO express the desire to connect in your first year of marriage, but DON'T be too apologetic.
If you are prone to guilty feelings, avoid talking to the not-invited too much before the wedding.
If you apologize too much, or give too many different reasons (stage fright! budget! venue! timeline!) it just reminds people that they aren't invited.
People are way more insulted by NOT being invited, than by having to turn down an invite because it's far away/expensive/whatever.
Also, apologizing too much gives the less scrupulous a signal that you feel guilty. Some guests may then work on you (or your mom, or your spouse) to make you feel bad until you invite them or whomever they're angling for (their kids, aunts, new boyfriends, etc).
Why you shouldn't over-explain
Two weeks before my microwedding, things got a little hairy. My hundreds of friends and family who WEREN'T invited were very accepting and supportive the first time I told them that we were having just nuclear family (and local friends who were “like family” to BOTH me and my husband).
I think I over-explained, giving too many different reasons, instead of Shutting The F Up about it until after the wedding was over. Thus, a family friend who's a pain the arse worked on my mom's guilt triggers HARD. We still didn't invite her (and I'm glad), but it was uncomfortable because my mom is a compulsive apologizer.
Having a short four-month engagement helped me out on this front – less time to waffle on the list. It also helped that my parents are planning a big, laid back anniversary party next year in their town (where I grew up – across the country).
Why you shouldn't blame the budget or the venue
Watch out for making excuses… Leaning on the budget or venue excuse is tricky. Miss Manners, whose philosophy is very “people first, money/pomp second,” advises to figure out the guest list FIRST, and then figure out where to host them and how to feed them.
She says that if you have a large list, it's better to serve punch and cake than to cut people based on dollars.
So if you try to lean on the budget or venue, expect that people might say (or think), “well, if you can't host all your guests there, you should find another venue.”