Old post I know, sorry

You'll have a blast at Little Sahara UT. I agree - with kids, you dont want to camp at sound mountain, but out near oasis/white sands - smaller kid friendly dunes.
Lagoon is a BLAST. Itll be hot, but not unbearable in July. You can always go in the evening, I think they stay open until midnight or slightly later in the summer time.
If you just want to do a water park - Seven Peaks in Provo is also alot of fun, but Lagoon has a really decent water park - but the lines to get in the water park are often long, since they restrict the number of people that can be in it at one time.
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'05 Polaris Scrambler 500 H.O.
10-56 weights with Polaris brown primary and TEAM secondary roller with HPD black/red secondary. HPD Air box lid mod, w/ K&N air filter. Stainless Pro-Circuit full exhaust. Ricochet swing arm guard.