On that basis Karen, there's never a good time.

As Young Athletes Team Manager at BBH I've had kids on holiday at every fixture. I thought they'd tried to block term time holidays, but it seems not!

Darwen is the final FRA Junior Champs race and with extra points this year (new initiative) it may well bring a better turnout - time will tell.

I think the main issues for the Lancs Champs secretary are :-
1. Identifying a Junior Race to piggy back for the Champs.
2. Persuading the organiser to incorporate them in to their race - they are not all compliant.
3. Where - is it suitable.
4. Does it clash with anything esle that might be a problem.

There's not that many options for venues really. How many junior fell races are there in Lancs?
Pendle in April would seem a natural choice; it has been the venue in the past - it was Easter Saturday though this year so your holiday issue would be relevant and there looked like there were more runners from Yorkshire than Lancs.
Stanhill - no I'm not serious, but pick a race like this and the numbers are always a worry - you need a venue that is at least going to guarantee decent quality races and organisation.

I think this year it was a straight choice between Darwen and Clougha.

Personally I would love to see it attached to something like Paddy's Pole as I think the venue is perfect for Junior Fell, but the main race is limited entry of 100 now anyway, it's a Tuesday evening which would make fitting Junior races in more difficult.
Perhaps setting up junior races attached to the Fiendsdale Race might be possible - but this year that clashed with English Schools XC so perhaps all the main contenders were away at that fixture.

A bit of a ramble, but it's more complicated than it seems.