I am planning to bring my family to spend Xmas and New year's with me in Dharan but they would be flying from the UK to Bahrain and enter KSA via causeway and then fly back to UK from Dammam.
Family would need an eVisa for entering Bahrain and a eVisa for entering KSA. I see Bahrain requires a return ticket in order to grant the visa but in this case exit from Bahrain would be via causeway to KSA. In the same way I believe KSA would want to see tickets from UK to KSA I suppose but in this case entrance would be via causeway from Bahrain.
Not sure whether the rules have changed but standard rule used to be that on a new (business) visa you had to arrive by plane in KSA. Any visits afterwards on the same visa, you could arrive via the causeway. From what I read, you need to have a visa that specifically mentions entry via air or land to allow you to enter using the causeway. See more here, but do double check: www.saudiarabiavisa.co.uk/saudi-arabia-bahrain-causeway/ Note also the paperwork requirements such as a Letter of Invitation from the sponsor.
This can be done assuming you mean the tourist e visa. You’ll need them to get biometrics registered on the causeway though for the KSA entry. There is an office just after the Bahrain passports checkpoint on the right side of the road. Make sure you have the tourist e visa bought in advance as will make it a lot easier. I’ve seen the booths broken for on the spot e visas so be aware.
In terms of entering Bahrain they may ask about where you will be staying and for how long. I’ve never had to produce evidence but I know others that have.
I’ve heard of issues where having to get an e visa cancelled if your family later wants to come via the iqama route can be a problem.