Serana appears to be the only follower I can take with me into the soul cairn. I want to use some of the destructive sunlight spells on the locals there. With Serana being a vampire this will undoubtedly do her damage as well. IF I can get her to change from being a vampire, will she still be able to acompany me into the soul cairn??? Will she then be safe from the restoration undead damage spells???

she will only change to a mortal AFTER the Dawnguard story line is completed. And only if you selected certain dialog during your talks with her.

and this would be best asked in the dawnguard forum.

Is there an easy way to move this or should I repost. I am a long time done with the Dawnguard quest.

Just click on the report button, and ask there that the topic be moved.