The Social Media Settings of the Crowdfunding and Peer to Peer Fundraising campaign type allow you to customize the default post message when a constituent clicks on one of the four social network buttons. You can find the Social Media Settings menu by clicking on the Crowdfunding keyword you want to change the share settings for, then by clicking on Social Media Settings in the left hand menu. You will be able to personalize the share message for Facebook and Twitter posts, text messages, and emails.
Write your share messages from the perspective of the supporter or donor by using first person pronouns like "I" and "My". Remember that the volunteer fundraisers and donors will be the ones sharing, so write it as if they did it themselves. This will easily provide your volunteers with marketing material to use in their fundraising efforts.