Single campsites allow one vehicle, but u can pay a small fee for a second. There is plenty of parking for both. No one actually counts how many people you have,but even if they did the baby would not count. We rented a double site because we had 9 people.
Some of the campsites have more space than others, most have very little space for extra parking...if any at all. So definitely book a double site if you need that... I don't think you're going to be harassed about group size unless you're causing trouble....especially if one is a baby. They don't check any of this when you drive in.
If you are reserving a single site, there is room for 1 vehicle. If you are reserving a double site, there is room for 2 vehicles. There is a small parking lot to the right (near 071) when you enter, but a few spots have signs that stay staff parking. I did see other vehicles parked there, but can't confirm they were being used by anyone who reserved a site. I can't comment on the group size. There may be a phone number on the reservation website you could call.
Thanks! Your answer is awaiting moderation.