Brenda
Where do you live?
You can get a lot of census info online. Lawson's site which is mentioned on this board has lots of IOM records on it. I tried to put in the web site but the filters won't allow it. I'll experiment with what will be accepted.
/www.iomfhs.im/lawsons/LawsonBMD/census/census_index.html
I have most of the 1851 and 1881 censuses.

I believe you are going to IOM soon. I would encourage you to do as much research that you can online and on the genealogy board. It would be a shame to use your time on the Island to look up information that you can get elsewhere.
Read about the Manx Museum in Douglas.
The IOM Fam Hist Society has a small library in Peel

I would encourage you to spend your time, seeing the countryside, meeting the people, learning about the culture.

Be direct on the board--when are you going, how long are you staying, what are the names you're looking for and what parish?
There may be people who live on IOM who would be willing to give you information about where to go, what to see, etc so that you can really maximize your visit.

I hope you have a wonderful visit. I, myself, haven't ever been there.
Donna