I *really* don't want to lead you astray.
Since it seems you have experience with PS, you will likely want to go back to using it in the future. There is tight integration between LR and PS (not surprisingly).
I personally love LR. For most of my photos, it alone is adequate. There are times I need PS. There are times I use third-party plugins. But the LR workflow works quite well for my needs.
I think LR is intuitive enough that it would be a wash in comparison to Photos. The benefit of working with it this weekend is that the things you learn along the way will be usable going forward. Learning Photos this weekend likely won't help you in the long-term.
Your specific needs regarding batch processing would also steer you toward LR as I don't think Photos can do that. The problem is that I personally *don't* batch process files in LR, so I won't be able to offer help in that regard. I do know that it is possible to export a group of files with all of the same export settings, that's something I do all the time.
If you decide to do a trial of LR, you will need to import all of the photos into LR (obviously). Save all of them on your desktop (or wherever else) and then import them into LR. Might be possible to plug your iPhone into your Mac and then LR will see it as a source. If you have "copy and save" set on the LR import, it will make copies of the files for your LR library. You can then delete the originals from wherever you stored them.
In LR, you can then quickly review all the images and assign star ratings to them (by pressing the 1-5 buttons when you have an image highlighted). I imagine that there are some images out of the 1000 that are crap and you don't want to share. You can then filter the images by star rating to only see the ones that are good enough to work on more and potentially post.
Again, I'm not sure how to batch process in LR. For any particular image, you can "copy" adjustments you've made in one image (in the development module) and then "paste" them into other images. For my own shooting at events, many adjustments (with the possible exception of white balance and sharpening) don't carry over well to other images.
Once you have culled your images (by using the star ratings) and pasted global adjustments (like WB and sharpening that likely apply to all of the images), then you have to go through each image individually. I would start by hitting the "auto" button in the develop module on one image. Depending on what it looks like, you may want to tweak it a bit by adjusting sliders. You can copy these adjustments and then paste them onto other images, but depending on the lighting this may or may not work well. You may also want to make other adjustments on individual images (a common one being "level" while making sure to click the checkbox to crop the image after the adjustment).
You can obviously go full out by tweaking each image in complex ways, but for an office party that probably isn't necessary. You aren't processing these images for printing on a wall in your home, you are looking for down-and-dirty edits that will make them look pleasing on a web page.
Once you are happy with the pics you plan to share, change the star rating to one higher for all of these images. Then change the display star rating in the lower right so it only shows these pics.
Then highlight all of these pics (click on the first and then shift-click on the last to highlight them all). Now right-click on one of them (I think it's control-click but it could be command-click) and scroll down the options to export.
In the export dialog you can make all of your export decisions for the group of pics (including where to export them to, file type to export them as, file size, export sharpening, etc.). I think there is an option to export for web, but I'm not certain.
You can also save the highlighted pics as a collection which will make it easy to access in the future and will also let you add other pics to the collection that weren't taken on the same day.
This is very much a crash-course to get you started. There might be some things you want to do that I can't help you with because it isn't a part of my workflow. Luckily the internet exists and google is a thing
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If you are seriously thinking about using Adobe products, I would suggest biting the bullet and signing up for an Adobe photography 20GB subscription tonight. Then downloading Lightroom Classic. I'm not sure Photos would be any more intuitive and some quick internet searching could automate some of your workflow in a way that Photos isn't capable of. But I'm not overly facile with Photos, so I could be wrong.
Best of luck!!