I agree with what other people gave said regarding there being a big difference between weddings/funerals and christenings.
I've never been invited to a church wedding but would attend one as the couple would have chosen to get married in a church, and are presumably religious.
I have been to funeral/cremation services which have been religious because that is all I have ever known, fortunately the only people I have known well enough to go to the funeral have been older so a religious ceremony was expected - I guess there are non-religious services available.
When I volunteered with an organisation, we were expected to attend a couple if church services per year, such as remembrance parade. I felt uncomfortable in church but attendance was expected. The best church service I attended was one where we had a child of a different religion with us, either parents or child didn't want them going in (child attended for the parade part only), parents weren't there so I was the lucky one who got out of the church service to sit outside with the child until it was over.
I would feel really uncomfortable at a baby/young child's christening (or equivalent). I feel that someone making a commitment to the church should be made of their own free will and I would be uncomfortable being part of, what I viewed as, an unfair induction in to that religion. If one of my friends decided to become religious and be baptised/confirmed etc and invited me to attend the ceremony, I would go as I would view it as their choice and they would be making it freely. I would probably decline an invite to a baby or young child's christening etc though.
I used to be quite religious and go to church every Sunday, from the age of about 11 or 12 for a few years. I can't really remember who made the decision, but parents or grandparents thought it about time my siblings and I got baptised. I suppose we just got swept up in it all as we were taken along to church and attended every Sunday for weeks and weeks beforehand. We were baptised along with another girl around the same age. She and her parents stopped going but we continued for another few years. We got involved in volunteering for the church and started helping out at Sunday school as we got older. I don't think it was called confirmation but we went to the classes for whatever it was called and then had that service. There were regularly christenings in the Sunday services, I think she babies except one man who was being baptised so he could marry (one of the women who attended church regularly) in the church. I stopped attending the church when I was about 17 or so and completely stopped believing in religion and I'm actually very anti-religion now. None of the people I saw be christened/baptised etc did it of their own free will or legitimately consented (and I include the man who was baptised as I believe he only did it so he could give the woman he loved what she wanted - a church wedding) and that bothers me. I think even we were coerced into it, I think we got swept up in the whole baptism thing and religion thing - I really can't remember being properly religious before then (we were taught we had to say prayers before bed but that was it) - I think it was being in church that made me believe every word in the bible was true. It actually makes me quite angry. I think the only time a baby or young child should be christened should be if they are going to die and it would distress the parents if they hadn't been christened (is it catholics who believe even a baby can't get to heaven if they've not been baptised?). If you were my friend inviting me to your baby's christening etc, I wouldn't want to say this to you but it is how I would feel.