Is Eurostar doing the direct train this summer? Cannot find how to book it in early July so considering flights, though I much prefer the train. Any Recommendations?
I think you are just too early. I see tickets for sale on the Eurostar website for trains during the spring. This is not an unusual limit. The French system, for instance, books about three months in advance (with some exceptions). There are good reasons to ride this train, so I would wait and keep watch. As you may know, these are big trains and run frequently.
https://www.eurostar.com/uk-en
Yes, there are three daily direct trains from London to Amsterdam, and rumours are that there will be direct trains from Amsterdam to London before the summer. According to the Man in Seat 61, tickets go on sale 180 days before departure so you are trying to book tickets too early.
My GF and I went from London to Amsterdam in 2015 by taking a train from London to Harwich, overnight ferry to the Netherlands then 2 trains to Amsterdam. It was very easy, relaxing and fun. You can get a cabin on the ferry with beds and shower. We left Liverpool Street station about 5pm and arrived in Amsterdam about 10am. You can find the info on this on The Man in Seat 61 website here.
https://www.seat61.com/Netherlands.htm#.VITk1yhiFFQ
RDJ