Book EVA Air Y thru Chase Travel , Add Lap Infant Later Directly with EVA?

Book EVA Air basis economy thru Chase Travel portal, add lap infant directly with EVA?

If someone have recent data point and confirm my plan is good, I would really appreciate it.

- Book EVA Air Y on Chase Travel to take advantage of the 1.25x and $50 credit, pay with points (not award ticket, I just have points needed to spend and don't care about value)

- Once the booking is confirmed, call EVA Air to add infant on lap and pay cash for 10% fare plus tax&fee

The reason I don't want to call Chase to book with lap infant is reading stories about system issue with OTA and the infant never got added to the ticket. Does it work as above or EVA will have a problem with me adding the infant on lap since I booked thru Chase?