Okay how do you bid a bridge hand like this

I was playing Precision with the kid last night.  We are starting to get our bearings although our system notes are only 4 pages, (along with about 20 pages from our former system for notrump auctions and the like).  But I have no idea how to bid a hand like this.  Red on white I held:

S K H K85 D KQJ109842 C 6

I had just been reading about a major team competition where at one table they opened 5D and at the other table they bid 1D and ended up in 3 making so perhaps that influenced my decision, as did the vulnerability.  I opened 1D.  Colin bid 1S.  Now what?  Well I thought since 1D is limited I can bid 3D.  I love it.  So that is what I did, 3D.  Partner bid  3H. 

This is what I though.  This is an ambiguous bid.  Normally bids like this should show a stopper and suggest a club weakness but what would he do the other way around?  Sometimes I could bid 3S as last train but no here.  So 3NT will be a bit of a shot. Is 3NT really the right spot?  I might not be able to get to my hand after setting up diamonds and surely one suit is weak.  3H is game forcing so I am bidding 5D.  I wound up in the same place I might have in one bid. 

This got doubled by someone who didn’t like our auction but it was an easy make.  Colin had SA109843 H 1093 D 3 CAKQ

3NT is not as good a contract since it can go down occasionally on a heart lead and sometimes on a spade lead when the hearts are badly placed and you can’t get to your hand (my fear).

Here is the kid on defence.  After the play to trick one Colin stopped for a while (which he rarely does having the fastest mind in the East) and then found the right defence.

He held S86 HK983 D KJ C AK985

I led an attitude D2 and dummy came down with

S AKQJ10 H 652 D A97 CJ4

Colin won the DK and returned a heart.  Let’s look at all the hands and watch what happened.

Declarer starts with 7 tricks.  A successful heart finesse makes 8 and a ninth can come from clubs or diamonds.  But when Colin switched to a heart at trick 2 declarer seems to be in trouble unless the hearts are both onside.  Declarer might expect the defence to take 2 hearts, a diamond and 2 clubs for example. 

Declarer does have another choice though.  Declarer could play the diamonds to be 4-2 with Colin having the DKJ.  Then finessing the HQ and playing AD and another works.  How likely is that?  Well I am known to have the DQ from the play to trick 1 (and the lead of an attitude D2).  The lead also does suggest I have 4, I think.  But perhaps it also makes me more likely to hold the DJ then the HJ.  A tough problem to get right.