You could get the ultrasound on dvd and during your speach just have it playing on a tv behind you? OR have pics of you and your partner on a board with an ultrasound pic and a ? near it, ask people to guess who they think it is? (you could do it on a slide show if using a tv)


SIL got little booties that said nanna and grandpa and gave them to them.
Where are you having your engagement party? If your at home you could put a sign on a door saying 'nursery' and see if anyone pays attention.
Could you maybe have some little pink balloons and blue balloons and have what will it be written on them, see how long it takes someone to notice???