We go to Elveden twice a year. I'd cancel the cabanas and the early check in. We tend to arrive around 10 am, there is usually a bit of a queue but it moves fast, park in the main car park (some times we've been asked to drive straight to the lodge, but you still can access it until 4pm).
We then head to the park and grab a coffee. Grab a meal deal for lunch from the shop, then we head to the pool. Swim for a while then come out and eat out on the first night. We get the cars by about 6pm when it's quietened down to unload. They also have restaurant runner which is like an in house food delivery service if you don't fancy cooking, it's not the cheapest but found the food to be good.
Or just order from a takeaway in Thetford and pop out or they will deliver to the security lodge.
Cabanas - there is plenty of seating in the pool and it's not like you get time to sit down anyway! There's too much to do!
We pick up a click and collect order from Tesco on the way and take a couple of pre-made dinners (pasta sauce etc) from home. The ovens are gas and a pain in the arse. Pizzas can burn on the bottom before cooking through 😂 the freezers are also small, just a freezer box within the fridge.
Get yourselves some microfibre or camping towels from somewhere like decathlon. They dry much quicker.
Take seed/monkey nuts for the bits and squirrels. Apples and carrots for the deer, you'll have a tonne of wildlife.
The whole park is cashless so if the kids are going to have pocket money to spend, think about ordering gift cards before you go.
There is a sweet shop there which is obviously expensive. I let the kids pick out sweets at Tesco before we go to take with us.
And don't book too many activities. Mine like hunting for pine cones, squirrel spotting, the park is fantastic and the beach (take buckets and spades). We tend to do mini golf and bowling, that's it. Night times if you aren't too tired mine love going night swimming, the pool is open till 9pm I think and it's usually quiet. Oh and the kids disco is good. It's in the leisure bowl on Tuesday, Wednesday and Thursday nights, 6-8.