Japan, Anyone?

My mum has always longed to visit Japan for the longest time. It is funny because up to 5 years ago, she didn't go within 5-feet of sashimi but after some persuasion, she is a convert now. Anyway, I'd promised to take her see the cherry blossom next year. At the same time, I'd invited my Dad - thought it would be nice as a 40th wedding anniversary present. And then VT said that he hasn't been before so I'd invited him also. With the 4 of us going, what I am to do with my 2 Bs? Surely we will be gone for at least one week - I don't think it is fair for me to dump both my kids with my MIL for such a long period. We'll most likely end up taking Bryan for two reasons:

(1) He is old enough to enjoy it, not necessarily remember it
(2) He can eat whatever we eat so I don't need to worry about his meals, as long as they are cooked

So with those decisions in hand, now I need to look for a reliable tour company. I didn't think going on a Free-and-Easy tour would be a good idea although it would be cheaper. Afterall, I have two elderly parents to look after plus a hyper-active toddler. So, if you have any recommendations, I would be grateful for some advice.

P/S: If you're wondering whether I had a huge bonus pay-out, or if I striked lottery, it's negative to both. I think I'd just realised that there are somethings in life that I needed to do sooner rather than later, before it's too late and I end up regreting.