I agree with you that it could be confusing to introduce italic handwriting while encouraging reading regular manuscript. For that very reason we have stuck with regular manuscript. If you are helping your child in reading/letter recognition it only makes sense to use the same script for beginning writing excercises. 4 and 1/2 is definitely early to begin regimented lessons, but no harm can come of spending some time with a special notebook, practicing writing. Especially if it makes your child feel like he/she is part of what the older ones are doing!
I would suggest making your child his/her own writing practice notebook and letting him/her decorate it to give a sense of pride and ownership (in a positive way). When your child wishes to participate, great! But I wouldn’t make it part of the structured lessons, just let it be available, oversee so bad handwriting habits don’t form and encourage his/her overall desire to be part of the learning process:)
Mamasong