I'm the secretary of a small SDC chapter, and we do everything to make spouses and others welcome and happy. Food plays a good part, whether pot luck, or restaurant, or even 'catered' church hall lunches (one such is an annual event, and it is a win-win-win). There may be many interests and we try to fit all in. It might be needlework of some sort, or quilting and the like. What about commissioning a work as a public raffle prize for a fundraiser? Some people are into woodworking and other decorative arts and skills--we try to fit in several displays/dioramas, and get people to talk about that and other hobbies, whether it be dog agility, flower arranging, geneology, ham radio, square dancing, various travels they have done, volunteer work in their community and anywhere in the world. We fit a summer meeting on Prince Edward Island with a music/sing along meeting, dancing after a BBQ, overnighting and then a car tour with judicious stops to see shops, talk to interesting people, visit small museums/craft wineries/lighthouses whatever. There is a fall tour, again an overnighter, at a very relaxed pace with plenty of stops to see old grist mills, natural beauty spots, and each one is in a different province each year. This way, everyone who wants to participate does so (maybe not every year, because our club covers 4 provinces and a huge amount of territory. On more than one occasion I have driven the Green Goddess (49 Kaiser) on a SDC tour, and other have driven other antiques/orphans, as we often have other interests as well.
You never know what will turn up. At one inn outside a National Park we stayed at, the owners had unearthed a photo of it from 1949, and one of our members has the same model/year (47 Champion) car, so we spent about an hour inside and out mocking up a 'then and now' picture, parking identical or similar cars in the same spots, and delivering a professional grade blowup with frame to the inn owners, as a 'side-by-side'. Another time at a seaside light house which contained a cafe and a 'beach glass' collection of before and after pieces, one member recognized a particular item and was able to add an NOS antique car lens to add to their diorama.
We always get new members or casual visitors to tell a bit about themselves--and we take notes and try to fit something of that into a future meeting, with their enthusiam and participation. We do get casual visitors, because we park the cars together (and since we have a hard core of the exec who always bring an antique car no matter what, which teases out a few more members to take the plunge and actually drive their cars, fancy that.) along with banners and club flags on the cars, and a sandwich board. We keep running into people who have a car, and never heard of the club or didn't know of the resources available, they have just been keeping up great aunt Lettie's car.
Sometimes, we arrange visits to older folk and/or club members who may not even drive their antiques (or even any cars) anymore, or don't get around much if at all, but love to show off their restoration handwork and collections from decades gone by. It can even be a movable 'picnic' to their place. So, everyone no matter their age and level of participation feels like they too can belong to the club, and they have something to contribute no matter what it is.
As far as meetings, we generally have a lot of materials on hand--tapes, videos, books and magazines, old photos and little bits of memorabilia or parts that people bring in, just to admire, be part of a 50-50 prize or small auction, or to borrow or buy.
I would suggest keeping every segment short, and provide lots of coffee&tea/chat/mingle time as breaks. We also hold our business meetings before general meetings, and then report everything back to the membership. Other than justifiably private little bits of exec meetings (maybe 5% overall, and usually just contentious details including background stuff), everything is reported and discussed verbally with everyone, and well also publish everything in our newsletter/online: financial, membership, projects, everything. It is out there for everyone to see, including other clubs and regional/national/international levels.