If you use slow film (100, 200 ISO) and don't make many air trips, you should be safe from fogging even if they inspect them with X-rays. The problem with X-rays, from what I gather, comes with faster film and with repeated exposure to x-rays.

So it all depends on how many boardings you are going to make, and which film you use. Personally I would bring with me only slow film, and buy locally the faster film, if needed. You can also have the film developed locally, film seems to be quite in use in Italy nowadays and I suppose the same is true for other European countries, you will not have problems in having your slide film processed.