I don't think you are going to find exactly what you want in those locations with those limited days

planning a family vacation for my husband and I and our two adult kids, 18 21. this is last minute. My passport has expired so we are limited to US territory. vacation rentals old orchard beach maine We would like a laid back, not too fussy atmosphere, great snorkeling off the beach, and some fun activities. (caves, ruins, fishing trip). there are so many hotels/resorts in PR it is hard to narrow it down, and VI looks like mainly beach activities. we will have 3 full days wherever we are, budget around 3500.00 for flight and hotel. going Columbus day weekend.
Have you priced out airline tickets yet? That may have a big impact on where you go and how much you have available for your hotel and meals. You don't say where you are flying from but generally it is less expensive to fly to San Juan than to St. Thomas.
With only 3 days you'll want to stay in or close to San Juan if you pick Puerto Rico or stay on St. Thomas if you choose USVI's (unless you can get a non-stop flight to St. Croix) in order to maximize your available time.
If you are getting a "package deal" it would be better if you told us what hotels/resorts are available vacation rentals old orchard beach maine in the "package(s)" you are considering otherwise many of the places we might suggest could be out of your price range or simply not available to you, besides we don't know how much you have left in your budget after the price of the airline tickets.
1) For info on hotels go to TripAdviser.com - use the "More" dropdown menu to select "Forums". Click your way to the island you want to research then use the "Jump to more specific forum" link to further narrow your search. Once there click on the "Hotels" link and you can find listing for all the hotels in that city such as San Juan or island if St. Croix or St. Thomas. You can sort by price/ star rating, etc. You'll find hundreds of reviews for each hotel. Pay particular attention to the ones available from your "package" vacation rentals old orchard beach maine vendor.
2) Consider staying in a rental vacation rentals old orchard beach maine condo - many offer similar amenities as a resort yet you'll vacation rentals old orchard beach maine have a multi-bedroom apartment instead of a single hotel room - perfect for families. Cost will be about the same as some hotels/resorts. You can also research those on TripAdvisor - use the "Vacation Rentals" vacation rentals old orchard beach maine link. Of course, these would only work if they are available to you from your "package" vendor or if you wanted to forego the "package deal" and go it on your own.
For your criteria of "We would like a laid back, not too fussy atmosphere, great snorkeling off the beach, and some fun activities." I would go with St. John, USVI. For your limited travel days, you will probably get the most of your vacation staying in Puerto Rico. Look at the El Conventoin downtown San Juan.
I don't think you are going to find exactly what you want in those locations with those limited days and budget. Any holiday weekend will be crowded and prices will go up. Compromise will be essential.