Hi,
Just wanted to let you know that I live less than 5 minutes drive from the Keukenhof in Lisse, Holland.
Usually, from the 3rd week in March, untill half May, many tourists come here to visit the Keukenhof, but also all the bulb fields in the neighbourhood. I was a little surprised to read that in April, they were shut tight, since normally that is not the case. This year, it was so warm during that time of the year, that it was difficult to keep them from outgrowing at the end of April. Most tourist buses are here around Easter, that is usually the best time to visit.
Now, the Keukenhof is 20 minutes away from Amsterdam Airport, 20-30 minutes from Amsterdam, 20-30 minutes from The Hague, 20 minutes from Haarlem and Leiden. (NOT during rush hours though.) Volendam would be 1.5 hour. Volendam and surrounding villages would be indeed nice to see as well - as a tourist.
If you do not want to stay in Amsterdam or The Hague, I would recommend staying in Leiden or Haarlem, there are trainstations, they are cities but smaller than Amsterdam or The Hague. If you would like to drive however, I would recommend staying in Lisse or Noordwijk/Noordwijkerhout. You could still take trains or buses to the cities but in this area it is really easy to drive.
In the "center" of Lisse, there is a small hotel with appartments which I am told, is very popular among Americans.
If you would like to have more information about anything, I would be more than happy to help you!