I'd say taxi for the four of you with luggage, especially if two of you are either kids or seniors. You don't have to arrange in advance. Just turn right after the track area, you'll find taxis just outside the doors on that side of the station. There will probably be a line and hopefully a dispatcher. If your French isn't good, have the hotel name and address on a piece of paper to show the driver. I'm not sure what the fare will be, I'd think between 10 and 20 euros. You'll pay a small surcharge for each piece of luggage.
The alternative is Metro, which is less expensive but longer and more complicated, including a change of trains. It's a good way to get around Paris unencumbered, but I wouldn't use it with bags from Nord to a relatively nearby hotel, especially with a group.
This page from the "Paris by Train" website describes getting from Eurostar to Metro at Gare du Nord. To find the taxis, turn right instead of left and look for the "Taxis" signs. Should be no problem.