Having flown Silverjet twice I can attest to the fact they are flatbed. The following is from their website:

"Sleep is our real priority on our overnight flights. So, drift off in our 6'3" flat beds with no announcements, overhead lights or cabin noise to spoil your rest. We will wake you up just 30 minutes before landing to ensure you have the longest possible lie in and we can even give you an express breakfast to take away."

I thought OP was looking to go in April, hence EOS does only JFK in April. They are giving a 10% discount on flts to EWR once service begins though if the trip is booked by 4-11. I believe the 10% is good May thru September.

Cheers