Being out of status for a brief period wouldn’t be catastrophic. The OP can (probably) file for adjustment of status as long as s/he is out of status for no more than 180 days as of the filing date [INA 245(k)].
I got the impression that the OP and their lawyer are aware of the urgency of the situation, and there’s probably a good reason not to file the adjustment of status right now. Maybe the parents need to renew their E-2 status first before filing AOS to avoid a gap in work authorization. Maybe the I-140 petition hasn’t been approved yet. Maybe they are still collecting the supporting documents for the AOS application (English-language versions of foreign birth certificates, police records, etc).
That’s clever!
One word of caution about the F-1 application. In order to apply for a change of status to F-1, you’ll have to request an I-20 from your community college. At that point your community college might reclassify you as an out-of-state student because F-1 students are generally barred from in-state tuition eligibility in California. I don’t know how your community college would handle the concurrent application for a change of status to F-1 and application to adjust status.
Small and moderate-sized businesses hire immigration lawyers too.
My impression about how common that is might be biased because it’s based on a German-language immigration forum. German investors might do the E-2 paperwork themselves but almost always hire outside council for EB immigration petitions (either for themselves or for their employees). I wouldn’t be surprised if E-2 investors from other countries might do a different risk-reward calculation and choose to proceed without a lawyer more often.