Galleries

I suggest going to DrupalGardens.com sign up for a free website. Export it for free to do what ever you want with it on your own hosting. This might be enough for your needs but you could try to custome merge and integrate with OpenPublish (Drupal 7 version) if needing that functionality.

DrupalGardens sites and exports have readymade excellent image handling based around the media module (drupal.org/project/media). This has a multiple image batch uploader where you can create a gallery and then select one or several images at a time for upload, just like on Facebook or Flickr, and you can add more photos later too. This should satisfy your need for being able to create and populate a gallery at the same time. As for slideshow, the DrupalGardens export comes with that built in - if you need some more help let me know.

You could installing the media module and configuring this up yourself but I would suggest to save yourself time needed to configure it, just start with the DrupalGardens export and alter this as you need.

For an even more advanced SlideShow you might consider Views Slideshow module which is more sophisticated.

Do you need any features that OpenPublish provides? You might find that with the Drupal Gardens export and Views (and perhaps adding in the very promising Omega theme, Panels, Panels Everywhere etc for your site layout) that this does most of what you want.

If you want OpenPublish features as well I would suggest supporting the project at the same time. You might want to consider merging your DrupalGardens export Drupal code with the OpenPublish (Drupal 7 version) to produce a hybrid of the 2. I propose to do this myself. I suggest getting Acquia Desktop to run your site locally on your machine to test for quickest results.

For the merge of OpenPublish Drupal 7 with a DrupalGardens export I suggest using the general visual Windows/Linux BeyondCompare file/folder comparison and merge tool to merge the docroots of the 2 distributions, OpenPublish (Drupal 7 version) and your DrupalGardens export (Drupal 7 based).

Then try to do some 'plumbing' with the merge of OpenPublish Drupal 7 with a DrupalGardens export- i.e. configuration,coding and debugging to get OpenPublish added code to talk to the media module via Views etc. so that they are integrated. this is what I would like to try to do when I have time. I suggest Komodo IDE for step by step PHP debugging (if required to debug code (i.e. for runtime execution problems you encounter), and if you can manage to get your Drupal site running inside the tool!). If successful propose your code to be added to the OpenPublish source!

But see also someone else who wants the media module in OpenPublish - anything useful you do regarding this please inform them: http://drupal.org/node/1402716