Non-Jewish & Synagogue Etiquette?

I'm a practicing Christian (Presbyterian) and my husband is agnostic, and we think it's really important that our kids have a solid religious education. I've been fortunate to attend several Shabbat dinners with friends, and have visited synagogues, but never during services. I'd like to take our kids (who are 9 and 4 years old) to visit a synagogue during services, but realize in trying to plan it out that I have no idea what I'm doing in practical terms. Is it worth trying to just blend into the crowd at high holy day services, or am I being a jerk for taking up valuable space? We're pretty progressive and it would be nice to find somewhere that generally jives with us, so...reform? Etc, etc. Any feedback or ideas would be greatly appreciated.