Social Media Post Design for a Charity Event

Design details: Hello, I would like to have a professional post designed for a fundraising Nordic walk that I am organising for the end of September. I would like the post to be suitable for Facebook, Twitter etc. We are Nordic walking Morecambe Bay at the end of September. It is also a social event as we are staying for two nights with fundraising event on Saturday and a free guided walk on Sunday. We are Midlands based (Coventry/South Birmingham)
Ideas for the visual style: Nordic walking, Morecambe Bay, Wildlife Trust (sorry no real idea, open to suggestions)
Extra notes: The event is to raise money for Warwickshire Wildlife Trust who have provided me with their logo, It would be great if the posts could be used by both myself and the Trust. My website is www.nordicwalknow.co.uk. I'm afraid that as I'm doing this free of charge for the Trust, my budget is low.