We go all the time to WDW. Your husband was very selfish for booking it and I’d be upset too. But you’ll get lots of people telling you that so I’ll give the practical side of it.
sounds like you’re staying onsite, the deposit is either fully refundable or something like £50pp charge, I can’t recall. This is unless he’s booked a package with flights in which case it’ll be more.
you said it’s the basic dining package? That will be the counter service. If you’re wanting to do character meals then yes you’ll need to take more spending money as these aren’t included, or you can pay to upgrade the dining package ahead of time for it to include table service (which includes character meals) personally we love character meals as it means we don’t have to stand in line to meet the characters in the heat, and it breaks up our day, we go for lunch in the cool and the kids meet some characters and get fed. But if you’re not fussed, the quick service dining plan will be fine, you wouldn’t need much extra spending money for food really, drinks yes unless you take them with you each day (I’d recommend getting a crate of water from Walmart for saving money and also utilising the free ice water in the counter service venues)
August is a month I personally don’t choose to go in. It’s too humid, too stormy and unpredictable and too hot. The evenings aren’t even cool. But at the end of the day thousands of people go in august and love it, it’ll be personal choice.
you’ll be using the on-site transportation everywhere which is free but you’ll need to sort out to and from airport (MCO is the closest airport but I know some carriers fly into tampa, so it’ll depend which he’s booked)
we do things like bippity boppity boutique when we are there, all their packages have the same level of care and magic, in that heat I’d take a light princess inspired summer dress for the girls with you, book the basic package so they get all the pampering and the magic but aren’t in a hot polyester dress.
you’ll want spending money for souvenirs, gratuity, if you go off site at all to do a shop etc but on the whole you can go out there with very little spending money and still have a great time on the quick service dining package.
But your husband is still an arse for booking it without you and even worse for telling your girls! My sister in law did this, put my poor brother in a right spot as they financially couldn’t afford it but he didn’t want to upset the kids, absolute dick move on her part!
you’ll have to make a judgement call. If you want to go but don’t want to go in august, December - mid May are the least humid months, I’d move it there.
oh one more thing, get to grips with the ride fast pass systems etc as if you want to use those then you need to budget them