Don't try and do too much - "today is Tuesday, it must be Belguim" kinda defeats the iidea of travelling by canal.
Personally I would trade
for conveniance - unless the plan definately involved some coastal sailing trips.
3 months is a nice period for the trip (not too quick - not too slow! - and June to Aug, plus or minus is pretty much the Northern European summer......albeit not exactly a rain free thing!.....so definately plan on some of that involving wet!).
Downside to the 3 month period is when it comes to a boat - IMO falls between renting
. Likely that a straight commercial
hire would be very expensive and that a buy would involve the aggro / cost / uncertainty of buying
, tweaking and then selling.........but might be worth trying for some sort of Owner direct rental, whether "formally" or not.
Definately worth doing though.