score:5
You may not need a guide specifically for kids, as all recent editions of Lonely Planet guides include little "family friendly" icons next to all listings that are considered family friendly, which means:
Indicates children are welcome and accommodated for through the facilities available (eg has change rooms, an elevator, flexible sleeping arrangements, childrenβs menus etc). Not used to indicate a child might enjoy a place (eg a theme park) β that should be clear from the review.
Most books also have a Travelling with Children chapter with various highlights (and pitfalls) for kids in that city/country. And while this won't help in your specific case, for older kids (8+), there's also the Not for Parents series intended specifically for kids to read and use themselves.
And, as a traveling father of a 1.5-year-old myself, I'll heartily second Grzenio's recommendation to book accommodation in advance. Kid-hostile restaurants etc you can always deal with somehow (take-away, one parent takes the kid for a walk while the other eats, etc), but conjuring a hotel room or crib out of thin air is a bit harder.
Upvote:4
I don't think that such a publication exists (yet), unfortunately.
What I usually do is spend loads of time on-line before (and during) my travel with Kids on trip advisor, travel forums, google, etc. to figure out all the details myself. Often I would contact the hotel in advance to ask if they have appropriate facilities.
Also, especially when (a) arriving late (b) arriving in a big city (c) travelling in high season (d) travelling in Europe - I tend to book accommodation in advance. It is a pain, and strips the backpacking experience of this sense of freedom you get when travelling alone - but it is a substantially bigger pain to look for accommodation for hours with a small, hungry and tired child.