I had a nanny (at about the same cost as OP) and two kids. One was in pre-k (which I wanted him to attend, since nanny was great but wasn't the same as a pre-k setting) and it was about $450/mo. - so let's say $30k (for nanny - not including tax payments at end of year) + $4500 = $34,500 (+ taxes and other costs asso. with nanny - more food and utilities needed at home during the day, gas for the car that we wouldn't otherwise drive, etc...)
Once older kid went to K, we decided to pay for before/aftercare for him and full-day pre-k/daycare for the younger sib. Now we're at the following:
$400/mo for before/aftercare (full-time needed)
$2000/mo for full-day daycare
$200/week (avg) for summer camp - we pay for about 6 weeks of camp over all
=
4000 + 24000 + 1200 = 29,200 (but NO TAXES!!!

)