We are looking to go on our first holiday together next year must be somewhere like spain (close ish) there will be 3 adults and 1 3 year old needing 2 different rooms, all inclusive, under 2 grand including flights.......
Not sure you will get an all inclusive summer holiday under £2000 for 3 adults and 1 child. We were looking for an all inclusive holiday for Easter 2014 for 2 adults and 1 child and the cheapest was just over the £2000 mark. Try 3 star accommodations and of course it depends when you want to holiday - the UK summer season lasts from May to October.
You could try the holiday village Tenerife and see if they still offer free kids places for next summer. If you need 2 rooms there is no way you will get that within 2k but the HV I mentioned has suite rooms so that might help
A 3 year old wont need their own room in summer. Child in bed and you on the balcony in an evening.