The materials you use will of course be dependent on your specific aims, but here's my shot at an answer. It's a bit eclectic (for which I apologize), but I think some eclecticism is in order for your particular class.

I think that in order to cover all the different material that you want to, it might be best to get an overview book like O'Grady's Contemporary Linguistics (fairly inexpensive) and supplement it with other freely available resources: https://store.macmillanlearning.com/us/product/Contemporary-Linguistics/p/1319039774

I would not get a textbook, even a cheap one, for phonetics & phonology. It could be interesting and helpful to spend a day with IPA and articulation, and then cover some basic English phonological processes relevant to e.g. accents, dialects, and second-language transfer-- without referring explicitly to phonological theory too much. As a supplement, maybe try discussing tone and stress placement.

Here's a webpage for exploring speech sounds at home; however, I think the lesson is best done with a chalkboard, print-outs of an IPA chart, and practicing sounding them out: https://linguistics.berkeley.edu/acip/

The Haspelmath book mentioned by NNOX Apps above is good, and doesn't assume prior knowledge; This open access textbook has a section on morphology: https://essentialsoflinguistics.pressbooks.com/part/main-body/. The approach I recommend is to just walk through examples of a bunch of colorful phenomena. Compounding is often fun. One thing you could talk about is compounding in Beowulf or Sylvia Plath's poetry.

A resource for explaining how to do syntax trees (in Minimalism): https://ling.auf.net/lingbuzz/004774

There are also some videos on YouTube by UA professor Andrew Carnie which accompany his syntax textbook (also mentioned above) and they are stand-alone lessons in themselves, but the later videos are more technical: https://www.youtube.com/channel/UCSEZ6duRxX6R25mhRO06QnQ

On the note of YouTube videos, Crash Course made a linguistics series last year, and people seem to like their videos in general; I think they have one of the clearer basic explanations of syntax: https://www.youtube.com/watch?v=eDop3FDoUzk&list=PL8dPuuaLjXtP5mp25nStsuDzk2blncJDW

Here's a "collection of topic guides" for an intro linguistics course, which you could use as an index for ideas to fill a lesson plan with material: https://ling.auf.net/lingbuzz/005885

As you know, the chances are that the more standard and up-to-date the material is (especially for syntax), the less interesting they'll find it. And often students will be suspicious of the reason for some concept or rule's existence, because you don't have the time to explain years of linguistic theory.

Other than the regular arsenal including Steven Pinker, John McWhorter, TED talks related to linguistics, NativLang, and Tom Scott, that's what I got. Also Gretchen McCulloch. Students respond better to these voices than e.g. Noam Chomsky, that is for sure.

(Hidden because I realized that the question was asked three years ago)

The materials you use will of course be dependent on your specific aims, but here's my shot at an answer. It's a bit eclectic (for which I apologize), but I think some eclecticism is in order for your particular class.

I think that in order to cover all the different material that you want to, it might be best to get an overview book like O'Grady's Contemporary Linguistics (fairly inexpensive) and supplement it with other freely available resources: https://store.macmillanlearning.com/us/product/Contemporary-Linguistics/p/1319039774

I would not get a textbook, even a cheap one, for phonetics & phonology. It could be interesting and helpful to spend a day with IPA and articulation, and then cover some basic English phonological processes relevant to e.g. accents, dialects, and second-language transfer-- without referring explicitly to phonological theory too much. As a supplement, maybe try discussing tone and stress placement.

Here's a webpage for exploring speech sounds at home; however, I think the lesson is best done with a chalkboard, print-outs of an IPA chart, and practicing sounding them out: https://linguistics.berkeley.edu/acip/

The Haspelmath book mentioned by NNOX Apps above is good, and doesn't assume prior knowledge; also, here's an open access textbook has a section on morphology: https://essentialsoflinguistics.pressbooks.com/part/main-body/. The approach I recommend is to just walk through examples of a bunch of colorful phenomena. Compounding is often fun. One thing you could talk about is compounding in Beowulf or Sylvia Plath's poetry.

A resource for explaining how to do syntax trees (in Minimalism): https://ling.auf.net/lingbuzz/004774

There are also some videos on YouTube by UA professor Andrew Carnie which accompany his syntax textbook (also mentioned above) and they are stand-alone lessons in themselves, but the later videos are more technical: https://www.youtube.com/channel/UCSEZ6duRxX6R25mhRO06QnQ

On the note of YouTube videos, Crash Course made a linguistics series last year, and people seem to like their videos in general; I think they have one of the clearer basic explanations of syntax: https://www.youtube.com/watch?v=eDop3FDoUzk&list=PL8dPuuaLjXtP5mp25nStsuDzk2blncJDW

Here's a "collection of topic guides" for an intro linguistics course, which you could use as an index for ideas to fill a lesson plan with material: https://ling.auf.net/lingbuzz/005885

As you know, the chances are that the more standard and up-to-date the material is (especially for syntax), the less interesting they'll find it. And often students will be suspicious of the reason for some concept or rule's existence, because you don't have the time to explain years of linguistic theory.

Other than the regular arsenal including Steven Pinker, John McWhorter, TED talks related to linguistics, NativLang, and Tom Scott, that's what I got. Also Gretchen McCulloch. Students respond better to these voices than e.g. Noam Chomsky, that is for sure.