Hello,
Before you buy a generator carefully consider what you actually need it for. Most sites these days offer mains hook ups, which will usually provide up to 3kW of power. By comparison the typical caravan generator will only provide 750W (0.75kW) of power so it is not a complete alternative to the mains hook up.
Modern caravans offer many items of equipment that are duel fuelled. Fridges tend to have 3 way power (12V dc 230V ac & gas), Water heaters and space heaters, 2 way (230V ac & Gas). There are many 12V dc/230V ac televisions & VCRs' available.
So if mains power is not available there is usually a sensible alternative to resorting to a generator. Gas is usually used for cooking, and makes a very economic alternative for water heaters and space heating. Fridges are also much more efficient on gas than on generator power.
For other appliance where gas is not an alternative, there are other low cost solutions. For example a 120W inverter (converts 12V dc to 230 Vac) will provide power for computers, radios VCR etc. So a generator is not really essential.
From a social point of view, generators are noisy. Even the "silent" ones produce some noise. They are very inefficient at converting fuel to electrical power (about 6%) the fuel is very expensive.
Gas appliances on the other hand are very efficient. They must be at least 70% efficient before they are approved for sale, and virtually silent.
The gas will already be on board for cooking, so there is no additional weight to be accounted.
Consider using a second battery that can be charged in the back of your car whilst you are travelling, and swapping when necessary. Or use the accessory circuit in the 12S (grey) socket on the rear of your car.
Do you really need a generator?