I appreciate the input from both of you. Lots of good points. Our daughter is potty trained and our son won't ready to learn those skills for some time so it would really be just the puppy we would need to teach early on. Our house isn't huge so we will all be spending the majority of our time in the same area where we can supervise our daughter with the puppy. I do believe that before long (as she approaches 5 yo) she will be capable of being with the puppy unsupervised for short amounts of time. She's kind and gentle and has been helping with her baby brother for the past 9 months. It's a very big decision and I'm not taking it lightly. I agree that at such young ages both the puppy and children deserve to be the center of attention. Both my husband and I are home working/ taking classes part-time. My hope would be that my daughter and the puppy would bond deeply and no one would feel neglected but rather my daughter would relish in the puppy's playfulness and the puppy would feel love and adoration from all of us. We aren't socializing at all right now. We go for a lot of walks and do lots of outdoor activities in the canyon near the river. My vision is that the puppy will just meld right into the fun
Yes I know how naive that sounds!
A couple of things to keep in mind. Until the puppy is 100% potty trained, which probably means until it is AT LEAST 6 months old or more, (probably older, because I am predicting that you will have less time to devote to potty training than someone with less irons in the fire) it will need ADULT, EYES ON supervision, EVERY SECOND it is out of its ex-pen or confined area to prevent accidents. That CANNOT be expected of a small child. At all. It just won't work. I can't tell you how many people have tried it with 15 year olds and it hasn't worked.
Even once it is potty trained, it will STILL be like a toddler... into everything, chewing up toys it shouldn't, chewing the woodwork, swallowing things that could hurt it... CONSTANT trouble. Because IT is a baby too.
As an aside on the potty training issue, I would STRONGLY advise you to look into indoor potty training. it is very common with small breeds in general, and particular with Havanese. ESPECIALLY with your situation with two small children, I think you will find that a puppy that understands how to go and use an indoor potty if someone isn't available to take them out is going to be a life saver. You can't blame a puppy for making a mess when he says he needs to go but you are up to your ears in a "kid problem". But every time a puppy has an "accident", whether it was his "fault" or not, it takes longer for him to learn NOT to have accidents. So if you can give him a way to avoid having an accident on his own...
As an analogy, you would never start potty training your child, and then lock the bathroom door so they couldn't get into it. Yet that is essentially what we do to dogs all the time. We really have no choice with large breed dogs, because we just CAN'T have them using an indoor potty. But by choosing a little breed, we can!
And don't worry that the puppy won't eventually learn to go outside. They ALL learn to do that quite naturally.
Second, a puppy should not be expected to go on "walks" of any length before about one year of age, or until its joints have closed. (it will ALSO first need to be TAUGHT to walk on a leash... they don't automatically know that either
) Now, in your situation, you might be easily able to get around this with a double stroller. Put your son in one section and the puppy in the other section. Let the puppy out to romp part of the time, and then put him back in for a rest. But EVEN IF HE SEEMS to be having a great time, over-doing exercise at that age can lead to premature arthritis as he ages. So don't over-do the fun now and overlook that you are raising a family member that may still be part of your family when your daughter is in college!