Definitely go through Big Sur - South of Carmel, North of San Luis Obispo. It's stunning. There are also places to camp if they want to haul a tent. Some of the cities are riding Air B & B - they are treating them like hotels so it's possible they could get hit with a "transient occupancy tax" - just be aware.
Our (Southern CA) Hostel network is pretty good - not as good as New Zealand's, but there are places. They're friendly and cheap. Remind them that taxes are not included in pricing of pretty much anything except gasoline. Get to the beaches - San Diego is great as well. To iterate - it can take up to 2 hours just to get across L.A. county - so choose drive time wisely. There are plenty of cheaper places to stay - Motel 6's etc. - and they get cheaper as you get further away from the coast. They should check out Sequoia National Forest if time permits. It costs $ to get into the park (unlike Big Sur) but it is ginormous and stunning - again, more camping opportunities. There are also fees for entering State Beaches - a day-use charge, usually about 20 bucks. Not all beaches are State Parks.
There's so much to see and do, if they're road trippin' it I guess they can only do the highlights but they should be fine in CA, can't speak for NV.
OH! I almost forgot! Come on down to Seal Beach and Sunset Beach and we even have great white sharks! Just like you guys!