I would disagree that the N810 would be a better device. A child is not going to have a relatively bulky tablet in their pocket at a party, but more likely the ubiquitous cell phone that he/she and all their friends will have. Furthermore, the internet calling option is only good if you are in range of an open wifi access point. Great in a dense city, but out in the burbs or the countryside a wifi point might be harder to come by.

How does Sprint's service work? When on the Family Locator plan, does the GPS in the phone always poll a satellite, or is there a message sent to the phone via the cell network, which then activates the GPS and returns the coordinates? Answering that question would be the key to whether a N810 would be suitable or not.