Can other people help me create a memorial?

Yes, there are two ways that people can help you add to your memorial:

Add people that can manage your memorial.
When you've created a memorial, go to Settings > People and you can invite others to help you manage it. They will be able to do everything that you can do including adding photos, stories and changing the settings for the memorial.

Allow contributors to the memorial.
All public memorials accept contributions, which you can then moderate to say whether you would like to add them to the memorial or not. You can make your memorial public by visiting Settings > Privacy and choosing the ‘Public’ option.