A method for calculating the field shift contribution to isotope shifts (IS) in many-electron atoms, incorporating quantum electrodynamics (QED) effects, is introduced. We also implement the model QED approach to incorporate QED contribution to the nuclear recoil effect at the high-order correlation effects treatment level. The proposed computational scheme is used to revise the value of the root-mean-square (rms) nuclear charge radius of the isomer of aluminum-26, Al26m. This radius is important for the global analysis of the Vud element of the Cabibbo-Kobayashi-Maskawa matrix. The difference in mean-square nuclear charge radii of Al27 and Al26m, obtained by combining the calculated atomic factors with recently measured isotope shift of of the 3s23pP3/22→3s24sS1/22 transition in Al, is 0.443(44)(19)fm2, where the first and second uncertainties are experimental and theoretical ones, respectively. The latter is reduced by a factor of 4 with respect to the previous study. Using this value and the known value of the rms charge radius of Al27, the resultant value Rc(26mAl)=3.132(10) fm is obtained. With the improved accuracy of the calculated IS factors, the error in Rc(26mAl) is now dominated by the experimental uncertainty. Similar revision of rms charge radii is made for the Al28, Al29, Al30, Al31, and Al32 isotopes using existing IS measurements. Additionally, atomic factors are computed for the 3s23pP3/22→3s24sS1/22, 3s23pP1/22→3s25sS1/22, and 3s23pP3/22→3s25sS1/22 transitions in Al, which can be used in future experimental studies