You will be fine v.t. No hyper planning needed for Universal. I always suggest people go to Universal Orlando website and go to bottom of the page and pull up the park maps. Look the parks over and get the lay of the land.
If you are staying onsite at any of the resorts you will have early entry to the parks. If you are staying at RPR, HRH or PBH you will also have unlimited express pass. This express pass works on all the rides excepts Forbidden Journey and escape from Gringotts.
Universal Studios and Islands of Adventure are very easy to navigate.
You will really enjoy the Harry Potter parks. Hogsmeade is in IOA. It has three rides the forbidden Journey, Flight of the Hippogriff (small coaster by Hagrid's cottage) and the Dragon Challenge coaster. There are some shops to go through there. The Three Broomsticks resturant is there as well as the Hogs head pub adjacent to Three Broomsticks.
Three broomsticks has a nice family feast meal that's a good deal for a family.
If you know you have problems with motion sickness ahead of time do what you need to do to sort that out. Forbidden Journey tends to get those with motion sickness. Escape from Gringotts not bad at all.
Universal Studios is were Diagon Alley is the only ride there is Escape from Gringotts. They have a lot of neat shoppes and the Ollivanders wand show. That's were they pick someone out of the group and let the wand pick the wizard. Leaky Cauldren is in Diagon Alley as well as Knockturn Alley.
If your kids love Potter would recommend getting them one of the interactive wands to do spells in Hogsmeade and Diagon Alley. It comes with map of spell sites. These sites are also marked with a metal medallion on walk in front of spell areas.
Hope you got the park to park tickets as you need these to ride Hogwarts express between the two Potter parks
MYTHOS is a great choice for a meal. You will like it. You can make reservations for Mythos on line at Universal Orlando site under dining. Three Broomsticks and Leaky Cauldren counter service. No need for reservation. There are some nice options at City Walk for meals also.
You can pull up all the restaurants in parks and City walk as well as the hotel restaurants and look at their menus.
To really enjoy the full Potter experience
1) have a butterbeer
2) Get a sweet from Honeydukes
3) have a meal at Three Broomsticks and Leaky Cauldren
4) have a ice cream at Florean Fortescue's in Diagon Alley
5) get pics of the fire breathing dragon spitting flames on top of Gringotts bank
6) get a chocolate frog with Halogram wizard inside
7) get some Bertie Botts every flavor jelly beans
8) get a Pygmy puff
Lots of fun things to buy.
Hopes this helps. If you have any more questions ask and someone will help.
Have a great trip