There are several ways to go about this and which one you choose depends very much on how you think about what you are doing.
Everybody needs to be able to meet with their clients in the space I should think, otherwise having a membership doesn’t seem that useful. Meeting with clients being part of the work. But having use of your space be (essentially) a perk that coworkers offer to their clients for free is a very different thing. It is a good thing in many cases, it is of course a good way to get to know new members and also it helps your coworkers to be able to show off a bit.
Your space is in a location we used to call “rural” coworking, that is, in a place less than 50,000 population, This number keeps coming up as a break point in terms of approach and in many ways it is still valid as such (though I think we will see some change int his as time goes on). In rural coworking, flexibility is all. Many basic notions about how coworking works have to be discarded to make a go of rural coworking I think.
It all comes down to what a membership is, doesn’t it? We have a “classes and workshops” membership, and I am not charging extra for the attendees because that’s what a class/workshop is. A part time or full time membership includes meetings because that’s what it is for, among other things. A return and pickup membership for online retail includes somebody at the counter or the loading bay to deal with boxes because that’s what it is for. You may have a disconnect between what your members think it is for and what you think it is for. This means you have to talk about it.
The options are many: you can have a membership which includes the right to invite your guests to use the space, and price it accordingly. Both a full time and a part time membership here includes this, the time guests use is simply counted as time the member uses. You can also have guest passes which members can ask for or that you include X number of as part of their onboarding.
You can also approach it on a pure “per seat” basis, in which case guests are treated just like coworkers. This works for Seats2Meet, but it is part of a whole model which is certainly worth looking at. As a piecemeal approach I do not think it would work.
For us coworkers are renting the whole spae on the basis of sharing it and everybody pays based on what they use, keeping i mind that whatever they are using is then not free to be used by everybody else as a result of that. So booking a desk is the act of letting everybody else know that you will be on that desk at that time, and that means as many people as you can sit at a desk, more than that and you are booking a room or part of a space. We work in in half day increments for this, and within that half day pretty much anything they want to do at that desk or in that room is okay with me so long as it does not bother the other coworkers. If they want to bring in the local footie team and a marching band for a half day, that’s fine as long as there are no problems with noise complaints and they bring their own beer. (You laugh. But somebody once did bring in a travelling circus).
Key to all this though is certainly getting clear to your coworkers what they are doing and what you are doing adn what the other coworkers aare doing as members of the space.