I have an iPad 2, it does not have cellular connectivity, it connects to the internet via wifi. It does not have an internal GPS. I purchased a Dual GPS, hockey puck sized device which connects to my iPad via Bluetooth. With this setup, I can use my iPad for navigation without having to connect to the Internet. This would solve one of your issues (navigation) but it does not address your need to connect to Internet to get weather info.
On our boat and every boat in TMM's fleet, a wifi router is provided at no cost. It provides Internet via the digicel cell service. There is no cost at all to the charterers for the service or the device. We have found it to provide relatively good connection speed ( email, web surfing, Facebook, etc) throughout the BVI's. It's not fast enough to stream video (Netflix)
Hope this helps,
Tony
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