I wouldn't risk it to be honest, you are probably still immune but is it worth taking the chance? If you did catch it it can cause problems with the baby. I work in a hopsital and nurses are advised not to look after patients with cp or shingles. If i were you I would rearrange and see your fil in a couple of weeks time
Ring your midwife and check. If you can't get hold of midwife tomorrow morning the phone nhs direct for peace of mind whatever your decision. FIL had it while I was pregnant and we avoided going, but if I remember rightly I was told it was ok if it was on a covered area and there was no direct contact.
my sis had shingles when I was pregnant with DC2. We were all due to be spending a family christmas together so we didnt really want to avoid all contact!!
To be safe, my sis put MASSIVE plaster & dressing over the site (was conveniently on her back, so covered by clothing too) and we were just extra careful with hand washing / not sharing towels etc etc.
Unlike chicken pox, which is spread from any body fluids (eg sneezing etc), shingles only spreads the virus from the actual shingles site - so if it is kept well covered you will be fine.
You can't catch shingles, you only get it if you have had chicken pox, its to do with a virus that lays dormant in your body and then at some time in your life may effect certain areas of your body, however I think that there is a small chance that you could get chicken pox from a person with shingles if you have not had chicken pox already.