The Horniman made the final 5 of the UK's best Family-friendly museums last year. There's a week or so left to nominate
From the site:
Kids in Museums is delighted to be working with the Guardian on the 2007 Guardian Family Friendly Museum Award. The Award is only in its fourth year, but already it is the biggest museum award in Britain, attracting more nominations than any other award. Most importantly, it is families who choose the winner - again, the only award where this happens.