Re:how I can send multiple photos currently stored on my iPad via gmail?
In the "Photos" app,
Tap "Select"
Tap the photos you want to send.
Tap the "Share" icon.
Gmail may have a limit on the Mb size of individual eMails that can be sent.
Two or three full-size photos per eMail should be ok.
If you send low-resolution photos, maybe you could send more, but they would be down-graded in quality.
If needed:
How to Add email attachments in Mail on iPad – Apple Support
____________________________________________________________________________________________
Re: can I send them so that they take up less space on the recipients device
eg smaller than the size they are sent as normal gmail ‘attachments’?
Yes. Here's a way to do that:
Discussion thread:
Reducing Photo MB size - Apple Community
Also:
You can make the file-size smaller for sending by compressing the photos into one zip-file,
though the files are uncompressed to normal-size by the recipient for viewing.
How to compress and uncompress files (scroll down for the iPad info.):
How to open ZIP files on your iPhone, iPad, or iPod touch - Apple Support
If you use iCloud, larger groups of photos (up to 5 GB) could be sent using MailDrop
Mail Drop limits – Apple Support. (Seems GoogleDrive may have an option like this too.)
Hope this helps :-)