I'll probably repeat everything that has already been said:
1) Is Kala a brand that offers pretty good quality at a great price? Would any of these be a decent ukulele to begin with?
Only if you get it from a vendor that includes set up or you are able to fix possible setup issues yourself. It can be really off-putting to buy a cheap ukulele and then bump into playability and sound issues. With cheap ukuleles the saying "buying cheap means buying twice" frequently holds true.
2) Are there other brands that offer under $70 ukuleles that I should consider? Again, I'm not wanting to spend much more than that. The less I spend, but still get decent quality that's fun to play, the better...any extra I save will allow me to get a little better guitar for my son.
I wouldn't buy a ukulele for $70. This is always a difficult topic, because it sounds kind of snobbish, but with musical instruments you get what you pay, and $70 is just not enough to get something that will give you a good experience. If money's tight, I'd wait another month or two and get something *used* for $150. It's advice I should have followed more often, but buying used is really smart because you can often get most of what you have spent back if you sell it. If you buy new and then sell it later, you can easily lose 40% or more of what you paid.
3) Does anyone use a pick to play the ukulele? I ask because I have the bad habit of biting my nails extremely short...didn't know if a pick might be easier since I don't have any fingernails or not?
Some people do, and I actually like the sound of it on smaller ukuleles when playing higher up on the neck (much better sustain and clarity with a pick). It's a different technique, though, and most ukulele players don't use picks at all. (I never liked the rubber or felt picks; regular guitar picks sound better to me.) Some people play without nails, but it sounds pretty dull and lifeless to me. Good opportunity to stop biting your nails on your picking hand!
4) Is there an online program that you would recommend? My son can't stand his videos but I kinda like the JustinGuitar videos.
Free ones? Nothing that's really comprehensive, but there are various beginner series. JustinGuitar has one for ukuleles, too.
5) I've got some pretty long fingers (not fat, just long)...would a soprano ukulele be fine to start with?
The one that appeals to you is the right size. I spent a lot of time on fretting over the right size for me, I bought sopranos, long neck sopranos, concerts, tenors, baritones -- going in circles a lot, went in circles, watched my preferences change repeatedly, coming full circle than taking another turn. Now I'm at a point where I feel it doesn't really matter. Getting started with a new instrument is always hard, and while size does matter to a degree, it's not the sole decisive factor of whether you'll stick with it: determination and enthusiasm and discipline all matter more. Personally, I'm back to baritone size (still have at least one uke of the other three major sizes), but nobody can tell you what's best for you, only what works for them. I prefer baritones and sopranos now, but I have not always had that view. If you don't know at all, I'd go with a concert sized ukulele.
6) Is it "safe" to purchase ukuleles online? I ask because the local music shops (ie: within 60 miles) don't have a lot of cheaper offerings. I don't want to order one and then get it just to find out there are things on it that need to be adjusted/fixed and I have no clue what to do.
Local stores probably won't fix anything that needs to get adjusted either, unless you pay extra for it. With a cheap ukulele, that's likely to be the case (intonation, etc). Like I said, I'd not buy a ukulele for $70, but would double the budget and then look for a *used* one (so you get a ~$250 instrument).
7) Is there a relatively cheap but good digital tuner that would work for both the ukulele and the acoustic guitar?
All cheap digital tuners are pretty much the same thing and usually work for both guitar and ukulele. It's hit or miss. I have identical tuners from the same maker and some work better than others. Most are fine, though, it's pretty simple technology.
8) What other information or advice do you feel like I need and/or should know?
Don't buy a new uke for $70.