I can help you with the naming history. In fact, I was there when one of them took place! I have done some research through newspaper archive and other internet searches. The Astroworld Hotel opened in December of 1968 and carried the name until 1977. By May of '77 it had changed to Astro Village. I think the name change and remodel coincided with when Roy Hofheinz was bought out in 76. I stayed at the The Holiday Inn next door in the summer of 78. The two hotels merged in late 1990 or early 1991. (Sometime between August 1990 and January of 1991) to become the Sheraton Astrodome. The outside part of the hotel was added at that time that attached the two. (The shops that were in between were now basically inside the corridors of the hotel like the travel agency etc.) The first time I visited the hotel after that time in the spring of '93 I too, was confused as to what had happened to the Holiday Inn. I was staying there in May of 1999 and checked into the Sheraton. The next morning, hotel workers had put banners over all the Sheraton signs that now said Radisson Astrodome. In fact, after room service had cleaned my room, they had covered with black tape any mention of the Sheraton even on the phone!
When I stayed there in May of 2004 it was now the Park Plaza Hotel. I asked some of the staff when the name had changed and they said it was during super bowl week in January of that year. They added it was a nightmare with all of the reservation issues. I think the hotel was in its worse shape around that time. It was in bad shape when I stayed there in 1986 as well when it was the Astro Village but I digress. The hotel changed to the Houston Grand Plaza in December of 2005 and to the Crown Plaza in May of 2008. I just stayed there the first weekend of the Astros season (a week and a half ago) and was surprised at how good the hotel looked. The hotel was reasonably priced. My only complaint was the bar drinks were very pricey.
A couple of other notes: My parents and I stayed in the Sheraton Motor Inn in September of 1969. It was very nice as well. Around 1974, it became the Astrodome Motor Inn. Sometime around the 86 Astros-Mets NLCS, it became a Days Inn. I think it was demolished in 2006. I think I remember that it was closed during my visits to the Park Plaza in 04-05.
Hope that helps. I am a little less clear on the chronology of the Howard Johnson on the other side because I never stayed there.
I was sad to see that the old Las Vegas Motel on South Main has been torn down. I stayed there once in 06 when it was a Howard Johnson. It was one of those America's Best Value deals the last time I drove by in 13 or 14. I was REALLY sad in 2001 when I drove past the Marriott on Braeswood and it was in the process of being demolished. That was a beautiful hotel back in the day!