Keep the hire car would be my advice. An early start from Vegas will get you to Zion State Park just about lunch time; plenty of places to eat just before you get to the park. Two hours or so should be enough in the park though last time we spent most of the afternoon there. When you are done head up towards Bryce and stay at Tropic (about 5 miles beyond the park entrance)which is a lot cheaper than staying at the hotels at the park entrance.
Next day up fairly prompt to visit Bryce which will take most of the morning. Return to Vegas via Cedar Breaks for a spectacular view. This will get you back to Vegas early eveningish.
Might be worth getting the pass that gets you into all the State Parks; "America the Beautiful - National Parks and Federal Recreational Lands Pass - Annual Pass for $80".
Valley of Fire is not a lot to see; just a drive through....well up and back. You can still see one of the sets there from the 1960's film "The professionals" (Burt Lancaster) there if that sort of thing interests you!. If you decide on the Valley of Fire combine it with a trip to Lake Mead; maybe even take a trip on the boat from Boulder City.

Thanks for your advice - it seems as tho it might be too far really - I wonder what else we could do for the last four days, we only do 'pool side' for a couple of hours and then get bored.

Could try a trip to Red Rock Canyon;, a nice afternoon drive.
Morning for a cruise on Lake Mead, visit the Boulder Dam and return via The Valley of Fire.
Calico. An old restored mining towmn on the way to Los Angeles.
A long day out will take you to Death Valley.
Visit the Grand Canyon overlook where you can walk on the glass floor out over the canyon.

Thank you busdriver - that's excellent advice. We're having further discussions.....

yup, Bryce Canyon is a loooong drive in one day, we set off for it last year and after a few hours turned off instead to the north rim of the Grand Canyon. It was a VERY long day.

TC

One other point to ponder; some of the hire car companies have restrictions on taking cars into California. I nearly got caught out on this myself. I think they are more concerned about taking cars into Los Angeles than Death Valley etc. Worth a check anyway.

Valley of fire is well worth a visit. It is quite beautiful. About 50 miles or so north of Las Vegas. $6 per car to get in.

HERE is a link to the State Park website.

you could do a loop around the grand canyon in 4 days which we did, Las vegas to Kingman Arizona, then onto route 66 for a bit, grand canyon for a night, then head to Lake Powel, stop at Lake Powell resort, then to Bryce and Zion, Zion Lodge is lovely, then back to vegas via Lake Mead, to be honest lake Mead isnt worth the visit but its not a bad drive!

I would opt for places closer to LV. A combination of the Valley of Fire State Park, Red Rock Canyon, Mt Charleston and Lake Mead would be a lovely day/maybe day and half away from the strip.

We went Quad Biking in the Valley of Fire which was excellent.

yup, Red Rock is nice and only just outside of Vegas, Lake Mead is great to hire a boat on, or like me - jet-ski! I love it

I'm gonna try the Valley of Fire myself this year

TC

I tried to add a couple of pictures of Valley of Fire. Couldn't do it. Sorry.