It would be so "do-able" for you to work interdisciplinary with the
classroom teacher in coming up with meaningful activities to teach a
little about these celebrations.
If children do not learn respect for other religions/beliefs at school
where will they learn it? You have the power to make change. Make
understanding beliefs part of your curriculum (it was a part of mine
and was written in curriculum guide - I hope it is still there - I do
know it is still part of social studies curriculum).