First off - welcome! We always like to see new people finding a creative outlet.
Next up, some of the hard realities. Most people find that they have the desire to create something but either lack the talent or the time or the equipment to do so to their satisfaction. The good news is that you decided to do something simple - if you can draw a circle, you can draw.
The next thing to get out of the way is money - you didn't mention it anywhere in your post, so I'm going to assume that you're not one of those "I'll do a webcomic and get rich" kind of people. If you're very lucky, you'll be able to cover the cost of making your webcomic, but the vast majority of webcomics don't make a dime.
However, if you're making a webcomic just for the pleasure of it, as a creative outlet or (as you mentioned) to tell a story, then draw away!
Okay, on to the serious business.
With two young children you will find it fairly hard to make paper versions of your comic and have them last any length of time. No matter how you lock them up, how high you put them, how carefully you hide them - the kids will find them. Kids are like that.
What I would have suggested would be a graphics tablet. These things are (relatively) cheap and reasonably hard wearing. However, I'd advise against getting one until the youngest is capable of knowing mine from thine - usually around ten or so. That, or be prepared to buy a new one every so often (which will get rather expensive really quickly).
Drawing on the computer with a mouse is quite difficult to say the least. Making a straight line (other than vertical or horizontal) is really difficult and drawing a good circle is a pain at the best of times. Plus it's counter-intuitive.
What I've found to be a good compromise is to draw the very basic comic (main characters, basic background) in one colour (I use black, most people who use this method use blue), get it into the computer (either scanned or photographed) and then go over the lines with the mouse in an art program (Photoshop, inkscape, MSPaint, whatever).
The better the software, the better your result will be. If you can't afford Photoshop, download GIMPshop (it's free, and pretty much like photoshop). Learn to work with layers - you can do amazing effects quite simply.
Other than that general advice, most of what you end up doing will depend Hn what works for you and what you have access to. Here's a short write up on how
Howard Taylor (used to) draw Schlock Mercenary which may help you.
Crossovers: First, get your comic going. If you don't have characters, you can't cross anything. Second, get some kind of archive going. You could try it when you only have three or four strips up, but odds are you won't be able to get much of a response. I'd suggest waiting until you have at least a hundred or so strips up (depending on your update schedule).
However, just when you do will be up to you. When you are ready to do a crossover, pick an artist you like and email them. Odds are that you won't get a reply (at least not straight away) but try and avoid email'ing a bunch of different authors fishing for a response. When you do get a response, you want it to be from a webcomic that you know the characters and backstory of.
Guest appearance: Similar to above, email the author of the comic with a short pitch on what you have in mind. It'll be a lot easier to ask to 'borrow' one of their characters than to try and get them to use one of yours.
Of course, you could just go ahead and use their character(s), but they might object, especially if you have them do something that they don't want their character doing And if they reply back saying that they don't want you to use their characters, respect their request.
Lastly: Practice!
What I've found has helped me is to grab two sheets of A4 paper, fold it in quarters and cut it up. Then staple the eight sheets in the corner into a little book-type dealy that fits easily in the pocket. Anytime I have a spare bit of time or if I get an idea, I'll either write something down or make a quick doodle. Even just drawing the tv while sitting on the sofa watching it will help.
The more you practice, the better you'll get.
, with more of a desire to tell a story than the ability to draw it well. With having a real life, cheap equipment, and children to destroy said cheap equipment, ive attempted to use some of the..err..computer art software 
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, so being able to do the obvious scetch-ink-scan-upload process is going to be outright tough (already had to redraw 4 strips that way). Yet trying to do the digital version of the strips will leave a bad tast in my mouth about how it looks. 
