I live 6 hours from Vegas and go quite regularly with my kids. We have a blast every time we go. My kids are now 20, 19 and 15. We were there in January, we've gone in every month over the last few years with the exception of December, April and November. Here are my thoughts (take them for what they are)
I'd rent a car just to help you get around easier. I would NOT park in the free hotel lots. I'd do valet, tip the valet person a couple of bucks when you are ready to go and get your car delivered to you. The parking garages are forever away from the actual hotel/casino entrance.
Do not let your "minor" child anywhere near the gambling floor. They watch those like hawks. We walked through when it was just my daughter and I and a person hit a huge payout on one of the machines and my daughter was about 2 feet over the "golden walkway" and they freaked.
Budget for meals is harder. You can eat fairly cheap if you eat at the food court/counter service type places in hotels. You can go from McDonalds, to Nathans hot dogs/NY pizza/deli to Margaritaville or much higher priced meals. I would say to plan at least 100 for food per day dependent on where/what you want to eat. For us it is a tradition to eat at the Paris' Mon Ami Gabi and eat outside so we can people watch and watch the Bellagio fountains. We usually do a later lunch so it's cheaper but closer to dinner so we just will need a "snack" later. There are so many delicious restaurants in Vegas. We also love the Italian Trevi restaurant in the forum shops at Caesar's Palace.
Things to do: Mandalay Bay's Shark Reef is really fun and we've spent hours there. NY NY Roller coaster,dolphin habitat,madame tussaud, venetian gondola or you can get the las vegas power pass to get unlimited entrance for 1/2/3 or 5 days to these attractions but it is not cheap. I believe the 1 day pass is $85.00 but to ride the NY NY Roller Coaster is almost $20.00 so...........the pass lets you get into these places:
BeatleShow!
Bellagio Gallery of Fine Art $16.00 per person
Eiffel Tower Experience $11.50 pp
Erotic Heritage Museum
Grand Canyon West Legacy Tour
Hoover Dam Motor Coach Tour
Hot Rod City
King Putt Indoor Mini-Golf $9.00 pp
Mid-day Lake Mead Cruise
Las Vegas Fashion Outlet Shopping Tour
Las Vegas Mini Grand Prix
Las Vegas Natural History Museum
Lion Habitat Ranch
Madame Tussauds Las Vegas $29.95 pp
National Atomic Testing Museum
Nevada State Museum at Springs Preserve
$10 credit at Planet Hollywood Restaurant (at Caesars Palace)
Putt Park Miniature Golf
Roller coaster at New York New York $14.00 pp
Siegfried and Roy's Secret Garden and Dolphin Habitat $14.95 pp
Sky Zone Recreational Center
Southern Nevada Museum of Fine Arts
Springs Preserve Las Vegas
Stratosphere Tower Observation Deck
The Mob Museum
Most all of the hotels have free things/shows to see and do. Be warned that there are porn slappers on every street corner handing out cards with "girls" on them and they end up on the street. Make sure your kids are prepared for that. They can be aggressive at times. We just put our hand up and keep walking. Don't put your hand out and just walk on by. You are not obligated to take them and I would suggest you don't.
It will be hot! It's a "dry heat" but it is hot and the strip with all of it's signs,concrete etc make it much hotter. Be prepared that things will look much closer than they are. Keep yourself hydrated, wear comfortable walking shoes, it's always crowded.
Disneyland is a 4 hr drive on a good day from Vegas. I wouldn't really want to do that if it were me but if you do a great place to get good rates is
www.getawaytoday.com
Please feel free to PM me if you have any more questions. I'm taking my daughter to Vegas in October for her 21st birthday.