i'm in the minority but i think the place is a blast. as stated above it's SLAMMED at night, i've never seen t-rex not crowded. we try and just grab a spot at the bar (no kids w/ us) but even that is tough sometimes.
as for lunch v dinner it's about what you're looking for. when the place is busy, the dinos are all fired up, the energy in the room is pretty cool. but if you're not in the mood for that kind of experience (or if you do not have reservations and don't want to wait a very long time) i would do lunch. we did lunch there once and it wasn't anything like dinner, very calm in comparison, like a different restaurant.
as for food i would keep it simple like a quesadilla or something 'bar food' related. the drinks are good and the take-home glass is nice