Welcome and congrats. We are a family of four divers as well and this is our 10th year of taking family dive trips with the "kids" now in their twenties. I don't have any nearby east coast suggestions but my suggestions are as you look to the Caribbean, you may want to look for places with shore diving as boat diving for 4 will get very expensive very quick. Costs aside shore diving can be more enjoyable. Bonaire, Curacao and Grand Cayman have been our favorite family destinations. Happy diving.