I would like to know if it is a violation of shabbat to have guests over who I know are going to drive home? If they come for my benefit to my home (but for their benefit as well) and I know they are reform jews who will always drive, is that wrong of me to have them? Is it any different than me knowingly allowing a jewish person to push an elevator button for me on shabbat for my benefit even though they are benefitting as well and would push the elevator button anyway? What is the difference? Are both wrong or are both okay? How "wrong" are they?
Shalom, The question of having guests over on Shabbat when you know they will drive has been addressed by many rabbis in the past generation. There are three major opinions - Rav Moshe Feinstein zt"l ruled that it is forbidden to invite Jews when one is certain they will drive (even if they could theoretically walk). He says this is a major problem of inciting Jews to sin. The second opinion is that of Rav Sholmo Zalman Auerbach zt"l who ruled that if you offer the guests the option of not driving, then it is fine to invite them, even if they do in fact end up driving. So you say something like "We'd love to have you over for Shabbat, and we can organize a place for you to sleep and stay for the whole Shabbat if you'd like. Would you like to come - even just for lunch?" Then even if they say 'Not for all of Shabbat thanks, but lunch sounds good" it is alright. After having offered them to sleep over and not drive, the choice to drive is not your responsibility. The third and most lenient opinion is that of Rav Moshe Sternboch shlita, who holds that as long as the guests understand that you do not approve of driving on Shabbat, it is fine to invite them, and the driving is not your problem. He rules this in cases where there is some long-term benefit for the guests in coming to you - such as them becoming closer to Mitzvot. I would add that the same is true if the invitation will strengthen family or community ties. All three opinions are, of course, valid. In the absence of a ruling from your local rabbi who knows you and the particular situation you are faced with, I would rule like the middle opinion of Rav Auerbach zt"l. The difference between this and the elevator case is understanding the meaning of "benefit". When the guests come to you there is no physical benefit you receive, apart from the pleasure of their company. In the elevator scenario you benefit from the forbidden act by using the elevator, which without the desecration of Shabbat would have been unavailable to you. This is forbidden on Shabbat. Blessings.