I'm not sure but there seems to be many complications with this idea. First, visitors on visit visas can do Omrah either before they enter Qatar or on their way out to their home country or to another country. They can't do it during the visit. Second, to be able to drive from Qatar to Saudi, I think you need to have a residency permit in Qatar. A visit visa doesn't work. Third, they have to apply for a visa to Saudi which seems to be an issue these days based on other answers to this question. Finally, it's much better to go for Omra with a travel agency (some agencies specialize in Hij and Omra trips - they are called Hamla). They advise you on what to do and provide everything: visa, accomodation, flights (sometimes ground transportation from Qatar to Saudi) and many other services that will make life easy, specially that it's usually busy in Ramadan in Makkah. You can find the phone numbers of some of these agencies in Marhaba or call 180.
I'm not sure but there seems to be many complications with this idea. First, visitors on visit visas can do Omrah either before they enter Qatar or on their way out to their home country or to another country. They can't do it during the visit. Second, to be able to drive from Qatar to Saudi, I think you need to have a residency permit in Qatar. A visit visa doesn't work. Third, they have to apply for a visa to Saudi which seems to be an issue these days based on other answers to this question. Finally, it's much better to go for Omra with a travel agency (some agencies specialize in Hij and Omra trips - they are called Hamla). They advise you on what to do and provide everything: visa, accomodation, flights (sometimes ground transportation from Qatar to Saudi) and many other services that will make life easy, specially that it's usually busy in Ramadan in Makkah. You can find the phone numbers of some of these agencies in Marhaba or call 180.
Best wishes.