Spot spray would be my first choice, but by mixing slighly weaker you could spray the whole lawn. Clover is difficult to control anyway, and I think it is mainly due to the way it repels the spray. If you spray when there is a dew on the leaves, your spray mixes with the dew and you will kill more clover. If you spray on a dry day with heavier mist or droplets, they seem to bead up and roll off clover but will still saturate the dandelions. You might have some damage to the clover but it ususally comes back strong.
I've spot sprayed a large lawn before, taking my time and doing 1/4 acre or less on a day, finally finishing a week or so later.