My thoughts on saving $$ and stretching your dollars:
1) Look for hotels at hotwire.com, but be aware of resort fees (which could be $25USD+/night) so read the fine prints carefully
2) Stay off strip. Everything is more expensive on the strip.
3) Buy coupons like Groupon and Travelzoo to save on food and attractions
4) Depends on the kind of cars you are renting, Turo.com might be cheaper
5) Some pools might not open til mid-April to make sure you double check with hotel.
6) Get your show tickets or dinner vouchers at the Tix4Tonight booth when you get there
https://www.tix4tonight.com/
That said.. if you dont drink or gamble, and not planning to go to any big shows (as they are $$) or eat at nice restaurants (also $$), there isn't much to do in Vegas. The Dam and Grand Canyon is only going to keep you busy for half a day (and it's SOO windy at the Grand Canyon you probably won't stay long), and maybe half a day at the outlet mall. Other than that I honestly dont know what else you would do with the kids.