It sounds like this is about him being out of his comfort zone - and understandably, as this sounds like a pretty full on trip for a 5 year old. Lots of new people to meet, and just as he gets used to one place, you're moving onto a new one.
So, it does sound as if you have planned a trip that would suit adults, rather than a 5 year old. Too late to change that now, but chalk it up to experience.
All 5 year olds say the odd tactless thing because they are still learning - everybody should know this and understand. He is persisting in calling you "grandma" because it is probably getting a reaction out of you.
Try to ignore the (minor) poor behaviour, praise the good behaviour and brief time outs for the unacceptable (for me, that would include throwing toys at TV, persistently not listening if firmly asked not to touch the camera).
Try to spend at least half an hour a day just playing something that he gets to choose and be in charge. That usually helps a lot with compliance through the rest of the day.
Good luck - you will both survive this!