How can I stagger each person to receive alerts one after the other?

Your SOS Contacts are initially set-up to receive their alerts as a group alert simultaneously (everyone at the same time), you can change that and stagger them to receive alerts one after the other or in groups based on time and type of alert.

Staggering SOS Contacts Alerts
The benefit of staggering alerts is that you can create a first responder, a second responder, a 3rd etc. therefore the others will never be disturbed if the first responders handle the SOS emergency alert, and if for some reason they miss the alert, then the others become your back-up.

Assuming 5 SOS contacts; Moony, Janet, Tracey, Paul & Jason.

Moony can be set as last on the priority list,

Janet (set-up as instantaneously) gets call’s immediately,
Tracey (set-up) 1 minute after Janet,
Paul (set-up) 2 minutes after Janet and
Alisha & Jason both receive their alerts 3 minutes after Janet.
All SOS Contacts are set-up to receive SMS’s and phone alerts and emails. 

If Janet takes responsibility before Tracey is alerted then the others never get alerted, if Paul takes responsibility before Alisha & Jason, then Alisha & Jason never get alerted and finally if no-one takes responsibility then Moony will be alerts at the end.

when adding or editing an SOS contact click on "Advanced Settings" 
Then select the "Priority" box and choose the delay for each one (see below)

How to send Alerts at available hours only

The benefit of this is that you use less credit as you only send alerts to locations or phones you know know the person is available at, also helpful if the service is used by a paid carer who only works between certain times.

Contact name “Moony”, he’s mobile number and private email can be set-up to receive SMS’s 24/7,

“Moony” can be duplicated with his home number to say, receive phone calls alerts between 6pm and 7am whilst he is at home,

“Moony” can be duplicated a 3rd time to receive phone calls whilst he is at work (work number) between 8.30am and 5.45pm,

Therefore, Moony can be set-up three times each with a different availability.
This means Moony will always receive an SMS and email immediately, and if he is at work between 8.30am and 5.45 PM he will also receive a call at work, if however it was 10pm at night, then the work number would not be called and instead the home number would be called together with Moony receiving an email and an SMS.