Just offer whole milk as often as possible. Try warming it up, try using different sippy cups (he is over a year old, right). ONce he really gets used to it start weaning off one feeding a day each week till they are gone. Nighttime will be the last ones.
It's a myth that babies need cow's milk while breastfeeding. They don't really need it, so if you child doesn't want it, I would just not worry about it. In fact, insisting that baby drink cow's milk could upset his sensitive baby digestion - which would make baby upset and cry a lot more.