Decide the dates you want to cross, look on the DFDS website for those dates and find the most economical crossings, then follow the instructions on the Tesco Deals website:
Take a trip with DFDS Seaways, one of the largest ferry operators in Europe and named the World's Leading Ferry Operator 2013 at the World Travel Awards. Use your Clubcard vouchers towards a trip and choose from Newcastle to Amsterdam, or Dover to Dunkirk and Calais. What you need to know
Vouchers can be used on departures until 14th December 2018 with a book-by date of 30th June 2018. Vouchers can be used for Economy fares and cars under 2.35m high only and can't be used with any other special offers or discounts.
Vouchers not valid online, you must phone DFDS on 0871 521 1538 to place your booking. All DFDS bookings on Newcastle to Amsterdam are subject to a £20 booking fee and £5 on Dover to Dunkirk or Calais. These fees can be paid for with vouchers. Maximum voucher redemption is £210 (including £20 booking fee, if paid for with vouchers). Only one voucher can be used per booking. It's advisable to book your crossing a minimum of 28 days before you want to travel.
However, I have a feeling that you can't use them for a crossing with a caravan - though I may be wrong and I'm sure others will clarify this. They can be used towards a Eurotunnel crossing with a caravan. Same thing applies, look on the Eurotunnel website, choose your dates/times and then follow the instructions given.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.