I think its a great idea!

As for when it becomes uncomfortable - well that depends on if she is suffering anything like SPD during the pregnancy, cos then she'd be uncomfortable from that time forward... I had it from about 28 weeks with DD1, but 4 weeks with DD2 - and don't have it at 27 weeks during this pregnancy. Plus if she's got morning sickness, she might not feel up to anything (not that I have anything to compare it to, cos I don't get morning sickness!)

Just depends on how her body copes with pregnancy really - she might be one of the extremely lucky ones and just glows the whole way through

Oh - and yes, I would go if my DH was able to watch the other kids for me with no problems