Jonno's question of the day ???

A

A & B both look like good options, but I am erring on the side of A, as that also removes the hassle of booking a hotel.

I would say that hotel accomodation is the best option. However there are possibly a few roboteers who will have to take any leave from work on an unpaid basis.
In these cases, maybe in addition to accomodation a modest fixed daily fee or help with travel costs could be offered from some type of 'hardship fund'?
As for a prize fund, personaly I have never considered it to be about the money and would much sooner have a nice trophy than a cheque.

The two biggest expenses for ourselves (besides the robots) are accommodation and - due to distance - petrol.
So based on that, my first choice would be A, for reasons most other people have already mentioned (takes hassle out of booking, group booking = good social gathering opportunity)
A set fee/daily appearance amount would be a nice luxury that could help towards our petrol bills but is not something I'd consider essential especially if we'd be saving money on accommodation.
A prize fund is an even bigger luxury but I'd be happy with trophies or even simply the excitement of coming first. That's partly what I do this for.

So in summary: A > B > C