elasta- i agree with ninah, you know he fancies you, and is keen to see you again, so i think you are fine to contact him whenever feels right for you :)
ninah - I wouldn't write it off simply because he didnt ask for your number, possibly he would have felt awkward doing so, or didnt want to put you on the spot, or maybe was thinking he would be more organic about it and get in touch via friends....any chance of those friends arranging drinks in the near future which you could both be at, or would that feel too staged? sounds as though you both got on well, and the fact he gets on with your dc is always a good sign. positive thoughts! (and good luck with the results for thurs, will keep my fingers crossed on both counts!)
mily - i'd like to think its significant but not sure...the idea he might like me seems a bit like one of those things which is too good to be true
re your night out, i think the main thing is to enjoy some time out with other adults, let your hair down a bit and generally have fun...and don't forget to have a big lunch beforehand :)