Mate, I am so glad to know that you and your daughter are safe.
First, Rattlers are often found under rocks and logs, particularly if the temperature doesn't suit them. So instruct your kids and other concerned people about it.
Rattlesnakes are typically capable of striking up to a distance equal to 1/3rd to half of their overall length, although longer reaches are quite possible.
Lets answer first things first.
If you encounter a rattler, how should you act, what should you do and what shouldn't you do? Do you freeze and back away slowly? Do you turn and GTFO? Do you dive for cover?
A snake sees (senses) you before you can see it, so be assured that it does know you are around. Thats why in most of the cases it will start rattling, but please note that when the rattle is wet, it makes no noise. Needless to say, If you see a rattlesnake coiled and/or rattling, that means it’s agitated. Keep away, Leave it alone. Wait for the snake to leave the trail.
Do not shout at it, it can't hear, it has no external ears like us.
Do not make sudden movements, instead back away slowly. Though Snakes do not see well, they have Jacobson's Organ which is an olfactory organ allowing it to process the chemical senses received by flipping of the tongue. Vipers, as they are called Pit Vipers have pits (looks similar to nostrils) to sense 1/1000th fraction of change in per oC. It usually perceives sudden movement as a threat.
Diving for cover doesn't make sense.
When will it strike?
Rattlesnakes, rather most of the Viper snakes, coil their body except for the forward part of the body which is raised. The body is a bit bulged up than normal and they usually buzz their rattle.
There is another persistent and common myth is that rattlesnakes always rattle before they strike, which I disagree to. Also, they don’t always strike every time they rattle.
Short story: It can't be predicted like that, you need to study them deeply. May be an experienced Herpetologist can predict better.
So, assume that it can bite anytime, so move away slowly.
what to do if you're bit
- Remain calm and first move beyond the snake's striking distance.
- Keep calm, panic will make the adrenaline come in picture and the blood circulation will increase, only resulting in causing the venom to spread much quicker.
- Dial 911 (assuming you are in US) or whatever emergency safety number you are authorized to dial.
- Remove jewelry and tight clothing before you start to swell.
- Position yourself, if possible, so that the bite is at or below the level of your heart.
- Do not let anyone try to suck the venom out of the bite site. (I have heard cases of such a horrid thing done, and the one who sucked also got to be treated as the venom in victim's blood entered the sucker's blood through minute injuries in his gum/teeth).
- Try not to make cuts around bite site as it swells. It will swell, no matter what.
- Do not apply any kind of disinfectant or tourniquet.
- Do NOT take anything by mouth such as caffeine or alcohol or any painkillers at all.