The biggest pain for us in our Chinese-English bilingual and biliterate journey over the last 14 years are:

1.  It takes a LOT of resources and time to create and maintain CLE (Chinese Language Ecosystem) throughout the years, in order to maintain their interest.  I have to watch a lot of Chinese videos with them as a result.  I was consumed with figuring out how to get more Chinese in for about 12 years.
2.  Similarly, it takes a LOT to provide Chinese instruction in sufficient pace to enable them to read comics or interesting books independently by ~ 7-9 years old.
3. It is extremely difficult to find local peers, whom you are comfortable with, for them to interact with in Chinese.  The most difficult age group is probably in the 8-13 years of age, when locally raised kids lose more and more of their Chinese proficiency.  By 8 years old, I would say 99% of heritage kids won’t or can’t carry a conversation in Chinese with another kid.  In high school, one can find teen immigrant Chinese speaking peers if one wants and needs to.
4. The logistics and cost of sojourn abroad and acquiring a Chinese book collection at home!
5. Devoting so much time to Chinese requires less time devoted to other extracurricular activity and requires the parents to take the long view (20-30 years).
6. They need to devote additional time for regular American cultural exposure and appreciation for friendship and peer interaction purposes, particularly around middle school years.
7. To ensure that dd#1’s Chinese is proficient enough for her to speak Chinese with dd#2, I didn’t work on her English much early on and she was more proficient in Chinese by age 8-9.  We had to spend a few years in upper elementary and middle school to “close the gap” in English.  That was a nerve-racking period, despite knowing that her English would catch up over time, based on the experience of youth immigrants.
8. With their education and Chinese language focused upbringing, they appreciate a much broader range of culture but often in less depth than functionally monolingual kids.  So, it can make it even harder to make friends with peers (particularly non-Asian ones) of different backgrounds who may have very different concern and appreciation, particularly as they enter middle and high school.  They have to look a little harder to find friends.
9. Based on the experience of those of my generation who were raised here, I knew from the start that this would be a difficult journey.  I couldn’t find anyone back in the early 2000s who “succeeded” to guide me, before the days of widespread internet use and creation of social media.  Well, I was wrong.  It turned out to be much more difficult than I had imagined.