If you really want to add Mexico, then skip some other things (like Vegas) and get on a plane and go somewhere nicer. Border towns are always iffy businesses.

Mexico - cancelled

Lake Tahoe : 2 nights

Vegas - I would be staying mainly at motels & 3star hotels on the West coast mostly as they are touching my maximum limit of USD200/ night (including taxes) and it was a breather when i checked Vegas and found that in $200/night i could live in a good 4/5star luxury hotel , so i would like to relax myself in Vegas and for this reason i am thinking of keeping Vegas at the end of my journey

Mexico - cancelled

oh thank goodness!

>>and it was a breather when i checked Vegas and found that in $200/night i could live in a good 4/5star luxury hotel

There is a REASON hotel rooms are cheap in Las Vegas in the summer! They practically give them away on week days and charge a little more on weekends. A room that is $250 in November or February and $500+ over New Years can sometimes be had for $50 in June/July/August. Ask yourselves 'Why?" -- there are reasons. Plus do note that almost every hotel tacks on a high resort fee on top of the rate and taxes so that bargain room may not be the bargain you think.

@Janisj - Vegas being cheap in summer has a lot to do with its temperatures of 40 centigrade. We are from a hot city (Karachi) and though we would surely like cooler weather but as mentioned previously that we do want to see Vegas once in our life. Its a worldwide famous casino city and we are coming from a far off country and wouldnt like to miss this opportunity.

I find California hotels quite expensive than the US East Coast, Australia and other countries i have traveled and i think Vegas can also give me a good good opportunity to taste some 4*+ hotels finally in this trip.

I do understand about the resort fees which is above the hotel rates and offcourse tax is being charged everywhere

The one hotel in Las Vegas that we stayed in more than one night was the Luxor. The sensation of going up on an inclinator to the room was a bit strange. The inclinators are in the corners of the pyramid.
At the south end of "The Strip" is a free overhead tram that connects several hotel/casinos.

@tumfuller - will get back on the hotels soon, but surely would like to stay closest to all the fun & I think it would be the "strip"

need recommendations on how and where to spend the 3 nights between SF & LA while traveling on the PCH1 (the scenic route)

>>Its a worldwide famous casino city and we are coming from a far off country and wouldnt like to miss this opportunity.

I honestly am not trying to talk you out of Las Vegas -- I am not a Vegas hater. I merely say that 4 nights is probably 2 nights too much.

For a property with moderate rates but excellent location - I'd consider the Mirage. It is well located on the Strip and walking distance from The Venetian (gondolas and 'Venice atmosphere'), Bellagio (the fountains), Caesars, Treasure Island, the High Roller etc.

I agree with Janis. 2 nights in LV is plenty and like the location, mid strip of the Mirage.

Mirage is nice, stayed there my last trip for a friend's wedding and has a very nice pool.

will get back on the hotels soon, but surely would like to stay closest to all the fun & I think it would be the "strip"

need recommendations on how and where to spend the 3 nights between SF & LA while traveling on the PCH1 (the scenic route)

"The Strip" (Las Vegas Blvd), is longer than you want to walk from one end to the other. If you are at one end and want to go to the other, ride "The Deuce" which is a double decker bus which runs up and down "The Strip" You can get a one trip ticket or get a 24 hour pass.
You do want to check out the "Fremont St. Experience" at the north end when the light show over the street is starting.
As for places to stop along the coastal route from SF to LA, check on Monterey/Big Sur and Santa Barbara.

The thing is one really doesn't want to stay on one end or the other because it is a looong way between. Mid-Strip is best for someone on a one-time visit. So places like the Stratosphere and Luxor should be ruled out - one is too far north - the other too far south. Moderately priced properties in the middle would include the Mirage, Flamingo, Harrah's, the LINQ. Of those I think the Mirage is the best choice. Others in the area (Venetian/Caesars/Bellagio) will all be more expensive.

There are also Premium Outlets in Camarillo..
which is on your drive between Los Angles and the Central Coast. Take your three nights and enjoy Santa Barbara and the outlets, the mission, the museums, the beautiful courthouse and the wonderful weather! You will save 12 hours of driving visiting these outlets rather than Vegas in the summer. If you DO go to Las Vegas, don’t miss visiting Hoover Dam. It’s amazing.

I would 1000 times take Santa Barbara over Las Vegas. It's beautiful, there is a ton to do there, great food, entertainment district, a zoo for your kids. I find people's idea of Vegas and the reality are a bit different. It's not really that glamorous, just a bunch of huge hotels far apart along a strip all with the same shops. The themes are fun but only for a day.

I would take pretty much anywhere along the California coast over Las Vegas! :-)

I never understand why people want to visit Vegas with an underage child. I know, I know, there are things for kids to do, but it's still primarily a very adult playground.

100% agreed its a Adult city and not child friendly. Even the hotels are not child friendly and especially for people like us who do not Gamble nor Drink there is nothing to do except room around and look around, but VEGAS has its own charm and people coming from far off after taking a 20-24 hour flight to reach California would like to see it once.

Santa Barbara, San Diego and PCH1 has its own beauty and charm but we always try to do a mixture of things in a trip and Vegas comes in it as an Extreme vibrant and unusual place to discover

Not sure where you are getting your impression of VEGAS being an extremely vibrant and unusual place to visit, for several nights in extreme heat, with a young child in tow, when you do not drink or gamble. As others have said one, maybe two, nights is all anyone needs of the Las Vegas experience. But what do those of us who have been there know? Stay hydrated.

Las Vegas does not have charm. It's an artificial city built in the middle of the desert for the sole purpose of luring gamblers and those seeking a hedonistic experience. But perhaps you mean something else by that word.

It's obviously your trip and you can go wherever you like, but there are so many more interesting and beautiful places than LV to visit in the southwest of the U.S.