Explanation for solubility of group 2 halides
To me it does not make too much sense to try to compare and explain the solubility (mass concentration) of anhydrous group 2 chlorides.

First of all, mass concentration does not seem to be the adequate physical quantity for comparison. Some of the chlorides have such high solubility that their saturated solution contains significant less water per volume than others. Molar fractions of solute and water would be a better choice.

Second, all of the chlorides precipitate as the hydrated salt from water. At normal temperature these are


$\ce{BeCl2\cdot 4 H2O}$
$\ce{MgCl2\cdot 6 H2O}$
$\ce{CaCl2\cdot 6 H2O}$
$\ce{SrCl2\cdot 6 H2O}$
$\ce{BaCl2\cdot 2 H2O}$
$\ce{RaCl2\cdot 2 H2O}$


Besides differences in structure their different stoichiometry makes a comparison difficult. And, most important, the formation of hydrates shows that we probably should not discuss the solubility of anhydrous chlorides at all.

Third, some anhydrous halides are more covalent than ionic compounds ($\ce{BeF2, BeCl2}$). This makes it difficult to argue with lattice energies and ionic radii.