I think both いらっしゃい (irasshai) or ようこそ (youkoso) will do. 'Youkoso' is stronger and more open. This is my perception of both words:
ようこそ (youkoso)
Man standing in front of a mansion and extends out his arms, saying "Youkoso! Welcome to my mansion!"
いらっしゃい (irasshai)
Woman standing at the door of a tea shop and bows, saying "Irasshai".
Haha... those scenarios above are what I perceive of those two words. And also, in my opinion, "youkoso" seems more used by men, while "irasshai" seems more used by women. But I'm NOT saying that those words are definitely restricted to the respective genders.
Anyway, hope it helps. =)