Your kids will have an absolute riot.
I asked mine what they wanted to do at half term? Butlins. So Butlins it shall be. This will be their third visit. DH and I have been to many adult weekends (we're there this weekend in fact 😄). That should be an indication of how much fun it can be.
We never get a dining plan because I prefer to eat in the other restaurants, so I can't comment on that, but the entire place is kept very clean and I found every member of staff couldn't do enough for us.
On the one occasion we had a problem with our accommodation (a blown light bulb had tripped the electrics), someone was there to fix it within 15 minutes at 8pm and I received a follow up call to check all was still ok the next day.
The shows are cheesy as hell but the kids were up at the front, bopping away, having the time of their lives. Absolutely no need to change in the evening if you don't want to, but my DD (8) likes to get glammed up. The tribute acts are generally very good, in my experience.
As a PP has said, expect to buy an annoying, flashing bubble gun that plays a hideous tune, but these aren't outrageously priced - about £8 as I recall, vs the $28 I was stung for at Disney world last week! And the refills of bubble mixture are £1 or less, from memory.
You can spend as much as you like in the arcades but my pair are quite happy shoving a couple of quid in the 2p machine and moving on. There is so much to do you won't be there for long.
There are a few activities that cost extra but none of these are extortionate. I think I paid £8 for DS to do archery but he got 45 mins or an hour of proper guidance and really enjoyed it. Some you need to pre book but there is no charge - they did a bath bomb making workshop run by the science museum once, which they loved.
Definitely download the app and build an itinerary. The stage times are released 7 days in advance I think.
There is a small supermarket onsite where you can buy the basics if you need anything, or there are proper supermarkets a very short drive away. In fact, at Skeggy, I think you can easily walk.
Have an awesome holiday.