I have known more than a few people in the past 10 years who have had kids at your age and things are absolutely fine. So congrats and please dont allow other people to effect your joy during this awesome time...
I have had two very very quiet almost cold techs during my U/S's for this pregnancy and I think some of them are just like that. Also, they might be nervous for you because technically the odds of their being problems are greater so they might just be very intent on measuring and making sure everything looks A ok.
There will always be someone who looks at you funny when you have kids later on (my first and second kid are 11 years apart and I am pregnant again) but just remember having kids later doesnt suit everyone either. So they might judge or be puzzled. The point is you are happy and awaiting a beautiful baby and you should just focus on that.
Congrats again

...