Yes, the fluoride is important and also at some point they stop getting enough of certain vitamins in breast milk (your son will soon be eating more and more solid food and less and less breast milk). IMO, and in the opinion of my ped, they are not yet ESSENTIAL but it's a good habit to get into at least a few times a week. Child won't be able to eat chewables until close to 3yo and believe me, at some point after you wean, your child will NOT seem to be eating enough and will need vitamins, and it is good to get them used to the drops.
And, again, the fluoride is important if you live in Portland.