www.visualistan.com|Weird plurals: Latin and Greek origins, irregular plural noun forms, etc...This infographic could be helpful for ELLs seeking to better understand these difficult grammatical rules.
This is a cheap and simple way to practice plurals with students: write the noun on the sentence strip, fold the right hand corner to cover up whatever gets taken away on the reform of the word, then write the new ending that makes the word plural.
This Link leads to a great activity for making dinosaur stomping feet for your kids! Obviously a better activity for the older toddlers, you can expect your 4 1/2 year old to be able to use irregular plurals, to refer to the 'feet' rather than foots. By 5, they should be able to talk about their daily experience, so get them to recount the making and wearing of the shoes to a friend or adult!