We have stayed at both Hard Rock Hotel and Portofino Bay Hotel. Whilst I liked both, HRH is definitely our favourite.
The HRH is the closest of all three of the resorts. Using the short-cut around the swimming pool, you can be inside Universal Studios within 5 minutes flat. The rooms are spacious (although not particularly large) and the service has always been good. "The Kitchen" is a great place to go for breakfast - it isn't cheap, but the food is wonderful and it is served buffet-style.
The pool at the HRH is truly one of the most amazing complexes. There is music piped in underwater and a slide and sand beach which my DS and DD enjoy. The pool bar is great too - and there is lounger service available. I would recommend hiring a pool-side cabana as well - a great way to spend an afternoon relaxing.
The Portofino Bay is more luxurious, with much nicer rooms. However, on both of our trips here we found the service to be appaling - with the staff having very poor customer service skills. Also, transportation is an issue. Portofino is the furthest hotel from the parks - and there are usually long lines for the bus service and water taxi. After walking around one of the parks, our three children were in no mood to walk the 10/15 minute walk back to Portofino. So, this meant queueing for the water taxi - and often the line took up to 30 minutes+
Having said all that, we do like the theming of the resort. The restaurants (again) are great, and the waterside is really beautiful. The theming is very authentic and once again the pool complex is wonderful. The villa pool is especially nice.
Our three children were 3, 5 and 7 on our trip last year. I certainly don't think that Universal is only for older children. There is definitely lots to keep older children happy, but there are still numerous attractions for little children as well. One of the best things about Universal Orlando is how compact the resort is - I love that you can easily walk between the two parks and citywalk, and back to the hotels if you wish.
There are quite a lot of characters at Universal, but my three only really enjoy seeing Disney characters! I remember seeing Shrek and the Cat in the Hat on our last trip. There were others too, but I don't remember their names! I personally think you will be able to keep your DD occupied for three nights. I don't know about your DD, but my three enjoy just swimming in the pool as much as visiting the parks

- so that's a good way to spend some time. We usually find that we visit one of the parks in the morning, return back for a swim early afternoon, then head back to the other park (or citywalk) in the evening.
I have a trip report for our HRH stay
here , and also one for our latest stay at Portofino (the link for this one is in my signature). HTH.
