He sounds wonderful, 100x, you will all have great fun with him. I am very sad about the fact that I am allergic to dogs as I love animals but it has made me go off them a bit. I spent my teenage years working as a vets assistant and used to alternate loitering as a grunger with cider, to sitting in a tree with James Herriot and a bag of boiled sweets. I developed the allergy as a teenager.
Franny -
I am afraid I disagree with everyone and I thought I might but here goes. You may be completely different, but I am not very good at being tired. IME, going from one to two to three, although you can't imagine loving another baby when it does arrive of course you do, and nature does make you feel slightly less precious about the older child, or at least it feels that they can grow up a little bit in your eyes. Of course this can be concealed from them as they often feel this is a good time to regress a little bit. All normal. They often turn to their dad a bit more, going to the park a few more times while you rest and so on. This seems to be the natural order of things with most people I know.
I have never told my children to stay in their rooms, as such, but after the age of 5 or so, they most certainly are aware that they must not wake me up at silly 'o' clock if I am to be a nice functioning mummy that day. This may be because I have had my babies with the same gaps as you, a 2 or 3 year old couldn't be reasoned with like that obviously. I talk to dd very nicely about it, I say that although she is keen to see me and I her, isn't it annoying that babies wake up so much and if I can have ust a little more sleep then I will feel better and she has read a book our put a tape on till, say seven, then I will be brighter and the day will be more fun.
I am aware that some might think this puts too much pressure on the child to think about how you feel when they should be being children, but I think they can understand this if necessary. In my case this was necessary. There IS NO WAY ON EARTH that I can be pleased to see a 5 year old at 6am when I have been awake with a baby between 3 and 5 and we have just gone back to sleep. I take my hat off to someone who can think oh well, if baby wakes up again we will all have a cuddle I really do. I cannot function. I made up for it in the day, I hope, now when they hear F is awake they all dive in our bed. The cuddles are still there.
I also think gentle encouragement to perhaps look at the time and think, hmm, it's 5.30, maybe I will play with my brio a bit more before diving in to see mummy and daddy can't hurt. I think 5 is old enough for that but I know people who get up with their children between 4.30 and 6am so, everyone is different. If there is any way that you might partially sit in my camp and be UNABLE to stick to this routine despite night wakings, then I think you should gently introduce the concept of reading a book in bed sooner rather than later.
If not, then fine, stay as you are. I'm sure the do nothingg camp works perfectly well and plenty have more than one child but, well thats my (lengthy) position on it. Oh, and ds1 brings me a cup of tea in the mornings. It's great.