This year is my 3rd Rotterdam in row Andrew. We usually go over on the ferry from Hull and stay with my wife's family in Schoonhoven so I can't advise on hotels etc. If you are in the South East of the UK then it's possible to go Dover to Calais and drive up to The Netherlands (less than 200 miles) You could even break it up with a night in Bruges.
The Expo doesn't have much to see or do and will only take an hour at most to get around so don't plan a half-day there.
The race itself is excellent with a rapid course and reasonable support throughout the race. It's not London or New York but it's not bad at all. The route is OK on roads and a tarmac path at some stage which might get crowded depending on where you are in the race. It can get breezy as well on the last 5 or 6 miles back to the finish and it's usually a headwind. The start can be a bit dodgy as I often see people sneaking up the pens to get away quicker and the stewards don't seem to bother about it.
If you do drive there then I would highly recommend a visit to Atlantis restaurant in Gouda. Gouda is a nice little town and you could actually stay there and get to the race quite easy. The restaurant is all you can eat but not like in the UK. The food is very varied and great quality (chinese, italian, american, japanese etc etc with all kinds of meat and fish) The only negative is that it can get busy so best to go early in the evening if you can. It's a great post race treat if you are up to it.
If I think of anything else then I will let you know
Was thinking about you the other day and your run streak. My mate completed a streak of 10 on Boxing Day. Not that impressive until you realise it's a streak of 10 years! Through wind hail rain and shine and his fair share of injuries!