i can't speak specifically for Dolphin games, however from other experiences with tickets and buying them the best option is to always try and get them through Ticketmaster (except for their stupid fees) or the team directly. Usually the cheapest option.
TicketExchange with the NFL and Ticketmaster is nice because it is season ticket holders putting their seats up for sale, but at their price and Ticketmaster STILL hits you with fees. A nice option sometimes.
Then there is always Ebay, Craigslist, Stubhub, and Ticket King which you play the gamble of thinking you got a good deal and then see tickets listed cheaper another day.
Lastly, is Scalpers. In MN scalping is legal so there are tons, but as the general rule of thumb goes with scalpers. The closer it gets to kickoff, opening pitch, face off etc etc, the cheaper they will be on their prices. If you wait like 5 mins after the game starts you can usually get a good deal as they just want to get rid of their tickets and make some sort of profit. However, I assume with two kids/teens coming down you would want to be in the stadium and settled for all of the festivities.
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