Welcome to the Dibb.
You're dates are similar to mine (19th to 2nd) and I've been monitoring prices for tickets and car hire for the last year.
I've booked carhire with Discount Florida car hire- Andy, who has been the cheapest for my dates and comes highly recommended on the Dibb.
Universal 3 park tickets were 219 pounds. Go through the links on the top of the 'Florida planning' 'Tickets' menu, to check prices on each.
Decide if you want to goto Volcano Bay, because if not, you'll only need the Universal 2 park ticket. You'll already have a water park included (Aquatica) with your Seaworld/ Busch ticket.
Do you mean to visit Disneys Hollywood Studios? If so, buy a day ticket in advance from Undercover Tourist. However, it will be absolutely heaving with Toy Story land opening, so personally, for the money, I would leave it for your next trip
Unfortunately your dates have peak prices for Universal hotels. The prices don't start reducing until 29th July.
Have a great trip - and get a countdown on the Dibb, from the list on the right 'forum countdown' !