I don't think telling or not telling is "weird". It's a personal decision that each person makes for themselves, and they shouldn't be shamed either way they decide to go. IMO. I do not see it as being more or less honest or connected to one's other children if you decide to wait--or to tell right away.
We chose to wait to tell our kids until we knew everything was in place, because we also needed some private space to deal with that possibility as well. My kids have had to deal with a great deal of transition over the last year. I was a full time student last year, and so for the first time was not in their school/classrooms every day, dad took over much of the carpooling and day to day care so I could study. I am no longer wholly revolving around them, and while they are all at a great age for that, it's a shift. This is another major, major transition for our family again.
And as I have experienced three early pregnancy losses, I needed to have some space to deal, before I could ask my children to deal. After all, unlike the last 3 times (pre-firstborn, then 2 when she was under a year old), I knew that if something were to happen I would need to be prepared to support three children through it. My daughter at 3 and 6 months last time really couldn't have cared less probably. :) What happens to me happens to my family, but I'm also a parent first, and for me that meant getting my own bearings first, as this pregnancy was *quite* a shock. My last pregnancy was so traumatic that I ended up getting treatment for PTSD for a few years afterwards, and some of that is resurfacing a bit (much relief to find out this pregnancy is NOT twins, that they could see), but thankfully in a managable way. So...it's just very complicated for me, but it's nice to be able to share info early, I don't think I could have waited until 12 weeks.
It was a risk in telling them at 8 weeks, esp. since I'm an older mom. However, if I have a miscarriage I also feel like it's valuable for the kids to see that it happens and frankly can be normal/common. If there's complications I'm also unafraid of explaining/working through that with them as well. It's been nice in a way to reopen those talks with my kids about sex, ect. (esp since they're 12, 10, and 10). We've been honest that this kiddo wasn't planned, but it doesn't mean that it's not welcome. I think that's important for kids (at my kids' age) to know, that you can get knocked up when not expecting it, and also that just because everything isn't 100 percent planned, it can still be just fine. Thus far the "was this planned" questions haven't bugged me, because...well, I think it's just a shock reaction in our case. I mean, our youngest kids are *10*. And I just started a business (found out I was pregnant 3 days after I signed my lease). But I guess it depends on how many more people ask me that. People who don't know my family don't blink an eye, because there are a crapload of other moms my age around here who are pregnant, so unless they know the context I don't think it would even be noticeable. It's not as irritating as the twin comments I got with my boys last time. Yet. ;> I've been getting crankier and crankier though lately, so who knows. :)
But yeah, when people ask if we meant to do that, I just say, "Nope, but we're looking forward to it anyway." Easier to do that when it's not irritating you though.