I just opened up an i 401k with VG as well. Timing of contributions (EE vs ER) depends on several variables but I think I read that EE contributions must occur within a specified time period from the salary deferral election for each paycheck (maybe a week or 2?), whereas ER contribution(s) dont have to take place until the deadline, which is filing date next year. How much and when we contribute to the i401K (EE vs ER) depends on ones personal circumstance.
with regard to fund selection, I have chosen the following:
VBMFX (total int. bond)
VFINX (S&P 500)
VDVIX (developed markets)
as admiral share classes are unavailable in the i401K. My total portfolio AA, however looks a lot different than that described above, but due to limitations set forth by VG (no ETFs, no admiral class), this was my best pick for my situation.
YMMV