Adding wireless speakers to my current, vintage analog system.

I think that you have some fundamental lack of understanding here, although you seem to be progressing.  I recommend reading the latest version about Hi Fi by Robert Harley.  He updates his book every few years and I don’t doubt that he has a chapter that covers the basics of streaming.  His magazine, The Absolute Sound, had a good series on basics a few years ago that should be easy to Google.

  So let’s try to be basic.  Streaming involves playing computer files through your Hi Fi system.  Those files are either stored on a commercial server (Amazon, Apple, Spotify, etc) or else on some kind of storage in your own collection, such as a hard drive or a usb stick.

   The files can sent via Ethernet, which is a wired connection to your Internet Modem/Router (I assume you know what a router is, since you use a laptop and are accessing this site).  Or the files can be sent without a wired connection.

  WiFi is the standard for wireless.  Hopefully you know what WIFi is. If you use your laptop to access the without being tethered to an Ethernet cable, or a cellphone, you are using WiFi.  Your HiFi system  does need a receiver for the WiFi signal.

  Bluetooth is another way to send wireless files.  Related technologies are Apple AirPlay and Google Chromecast.  In general you need a sender and a receiver for these as well.  Bluetooth and AirPlay in general compress the original WiFi signal and are of lower Fidelity than straight WiFi.  WiFi and Ethernet in general are equivalent and uncompressed and the best sound.  I am speaking in generalities here and you might get others disagreeing with some points.

So then how to stream?

You have a laptop. In theory that is all you need.. The laptop can take the files from a storage device. Laptops also have DACs. A Digital to Audio Converter converts those 1s and Os in the digital stream to analog sound. All you need to do is run RCA cables from the laptop into your ancient receiver. You are done.

Laptops have DACs, but they aren’t that great. So you can greatly improve things by using a separate DAC. The simplest way to go here is a DAC that looks like a USB stick and attaches to a USB slot in the laptop. The other end of the DAC has an attachment for a RCA cable that will attach to your receiver.

You then need a subscription to a streaming service, such as Spotify, from which you can get files to play. Or you can play your own CDs or lps, but you have to store them on a device as digital files.

Streamers are dedicated audio components that are basically computers optimized for computer audio.

Bluetooth is a convenient way to wirelessly send audio. Most wireless headphones or ear buds use Bluetooth as do many other devices. You need a sender, such as a cellphone, and a receiver, and a DAC. Some laptops can receive a Bluetooth signal. Bluetooth uses only a portion of the WiFi band so historically it has sounded inferior (but good enough for most non audiophiles). There is a new codec out for Bluetooth, which I haven’t heard, that purports to be lossless, but many devices, such as cellphones, are not equipped with that codec.

Ultimately I would recommend that you get a streamer and a new audio amplifier. You can buy all in one, AVRs that come with DACs and streamers included, but I wouldn’t recommend starting this way

I neglected powered speakers.  These basically have a pliers inside them, and then they typically are configured to accept Bluetooth, WiFi, and Ethernet, and usually you can plug in components such as CD players or turntables.

  So if I was you, You want to start with a defined budget.  It’s easy to fritter resources away when you don’t understand the concepts, or even when you do.

  Start with the laptop and USB DAC attached to your receiver.  Try a streaming service such as Spotify or Qobuz or Apple.  If you want to listen to your CDs as computer files we can help you with that.

  That might be all you need.  If you decide to go further, fine, but familiarize yourself with streaming in this low cost fashion

Thank you, mahler123, for laying it all out for me. 
It's not as bad as you seem to think. Some of the concepts I'm familiar with. But I did get confused, and it explains some things – and it may help me to decide how to approach this. 
What it comes down to is that I seem to suffer from first world problems:
– dreaming up things and being impatient about making it a reality
– assuming for tech to make anything possible, better, more convenient
– too many options
– expecting one thing to solve it all
– expecting high quality to be somewhat affordable
– constant upgraditis
– no time

My last post under powered speakers, should read “amplifiers “ and not “pliers”.

Questions you should ask yourself 

Have you defined a budget?  That should be step #1

Do you intend to stream solely from a service such as Spotify?  Or do you also want to move your CDs to a hard drive and be able to stream them?  Digitalizing lps is a whole different ball of wax.  Do you want to use a phone or tablet as a source and control, or be sticking with the laptop, or both?

 Further recommendations would depend upon your answers.  In the meantime I would consider getting a USB/DAC for the laptop and just streaming with that for a while to get comfortable.  Many audiophiles find that is enough and stop there, and it would be a low cost way for you to start