Re: getting on and off. I find it's fine, as long as you get them on right before going, and take them off when you stop. (You need to have the bike resting against something while you do this.) What you can't do (but I keep doing), is leave a child on the bike while you just fetch one thing from the house etc.
With two kids actually on the bike (not with a trailgator etc), the other problem is actually getting your leg over the bike. I've only ridden with two kids actually on the bike once or twice, but getting myself on and off was more than a bit tricky. I'm sure you'd get used to it, though.