http://www.johanniterorden.dk/gb/historie/1a.html
The Danish really participated to the crusades.
" The role of the Irish in the earliest crusades is vague. Most likely there were Irish involved, but probably under the banner of a foreign liege. Historians have commented that the Irish in the early years of the crusades to free the Holy Land were too busy fighting at home to organise a native delegation, but the early chronicler Guibert describes the first Crusade as containing an organised effort. "
From
http://www.louthonline.com/html/louth_crusades.html
Therefore i don't think they should be allowed to launch crusades. Anyway, feel free to mod your game.