I think that paying $4,600 to break the lease will be a drop in the bucket with what you'll save in cheaper rent and cheaper daycare in PG or Silver Spring (just outside the Beltway).
You can find childcare homes in Silver Spring for as low as $200 per week per child (including infants), so you can spend as little as $1,800 per month for your two children and have care from 7 AM to 6 PM. Centers in Silver Spring cost more with costs starting at about $1,200 - $1,300/month for your 2.5-year-old and about $1,500/month for your infant, for a total cost of $2,800/month.
You can find 2 BR apartments in safe areas close to cheaper day cares for about $1,800/month.
You can find lists of licensed Maryland day cares here:
http://earlychildhood.marylandpublicschools.org/families/finding-child-care/early-care-and-education-program-lists and you can use a mapping tool here (that for some reason doesn't include every daycare on the list):
http://geodata.md.gov/mdcc/
I know it really stinks you're stuck in a lease, but you may want to just cut your losses early so you can start working.
If it helps, Bright Start Daycare on Embry Street in Silver Spring just advertised last night to a local listserv that they have at least one opening currently. Their CareLulu listing is here:
https://www.carelulu.com/childcare-in-silver-spring-md-20902/bright-start-daycare-silver-spring/520881 and their Facebook page is here:
https://www.facebook.com/Bright-Start-DaycareLLC-176136772556896/?ref=br_rs . I don't know anything else about the daycare, but CareLulu says it's $300/week per child (which is a little more than many other places charge in the area), but at $2,700/month, it would be much cheaper than your DC options, and it would still probably be worthwhile to break your lease.
Relatively recently on this forum, Heritage Child Care Center in Hyattsville advertised that they had open infant spaces, and their costs are relatively reasonable for a center in the DC region.
Good luck!