I would not choose to take a Nich 31 to the top of the river. Not on the neap tide you will have. There are no visitors bouys up there. You can anchor or try the wall. Very little water.
I would rather go to Gins Farm. Give Royal Southampton YC a call and they will give you the details. They can also sort you out with a mooring.
The Bold forester is a bit of a long taxi ride from Beaulieu but if it is a nice evening the kids playstuff is good. Loads and loads of slides on bark chippings. Beware of broken grass around the outside tables. They could really do with redecorating the inside of the place though. Its getting a bit tired. (I live 5 mins away and have a small child you see).
Agree with other's comments about the restaurant at Bucklers Hard. I've been twice and the food is not good, but quite expensive and the staff seem to think that if they are surly enough and speak with a pretend french accent, everyone will believe they are actually at quite an upmarket eaterie. They are not. The restaurant in the pub is even worse. Suggest M & S ready-meal on board as it will be about the same, but a quarter of the price.
Very few boats get up there unless there's a rally on (Cornish Shrimpers up there last week) Nice trip in tender though if the old mother ship is too long in the keel.
Dont worry about paying, you wont get up river without being challaenged by HM.
As far as I'm aware the whole river belongs to Beaulieu estate and is managed by the Beaulieu River Management Co.