AMS is the main hub for KLM, Delta also considers it a hub due to their close partnership with KLM (Both are Skyteam). There is a non-stop flight between IAD and AMS.

You have a few options:

1) Build up a big Skymiles balance or transfer AMEX MRs and travel out to AMS direct by booking a seat on the KLM flight

2) Build up Citi Thank You, AMEX, and/or SPG point balances and transfer out to Flying Blue and book your flights directly through the KLM FF program.

3) Build up a balance with another SkyTeam Member (Korean Air an option if you have a lot of Chase URs) and go that route through to KLM again.

Either way, you end up on that KLM flight unless you want to connect in NYC or ATL. My suggestion would be a few AORs to get the AMEX and Citi TYP balances nice and healthy then transfer over.

It will cost you 125k miles per person.