PenelopePipPop and MsVestibule...I think I love you! 
Fwiw, my Dm has 9 siblings. They all have partners, and children, and most of those have children, all of whom I see regularly and love dearly. DP's father also has a large family, and DD is the first grandchild on his side.
We waited a long long time for DD, and to be honest there were many bleak times when we thought we'd never have a child of our own, so I think people were even more pleased for us than usual when she made an appearance. Both our families were immensely supportive, and put up with my longing looks at their babies, let me take their kids to the zoo etc for years, they were all over the moon when I eventually fell pregnant! How then could i not include our entire family in her Baptism?
I've invited lots of people because they are family and they all love her, and I know they'd like to share her day not to rinse a few quid out of them! I feel quite sad that so many of you have jumped to judge me without actually knowing me, and often without actually reading the whole OP. :(
As for the poster who asked, my motive was, purely and simply, that she has plenty of clothes and toys, and a family bible, and a money box already. I only have a small house, and rather than but gifts that she is too young to want/doesn't need just for the sake of buying something, surely it would be more sensible to put it in a high interest account towards a car/house deposit/university for when she's older, or alternatively, another poster suggested that we could ask for a donation to charity instead, which I also thought was quite a nice idea, since at this point in her life she has everything she needs and plenty of other children are far worse off.
However, all of the above was only ever going to be mentioned if, and ONLY if, someone were to ask me if there was anything she would like as a christening gift, face to face, in a conversation like manner. As it happens, one of my her aunties sent a text asking exactly that this morning. I replied "What she would like best is a big cuddle from Auntie X, and maybe a matching kiss from uncle X. See you at the christening, love Balloon."