Contact Bradt (travel guide co) to see if they can sell you their Liberia travel Guide/look for second hand copies. That ought to give you a feel post revolution, but pre-Ebola. Apologies if I have misread your post, but I am not sure that you are visiting as a healthcare professional.
I hope you have been given sufficient information by your church/charity to enable you to make a sensible decision.
Have any of your aspiring passengers (in the UK) done any travel in sub-Saharan Africa? Or anywhere else where you have to "make do"?
Can any of you fix cars/change wheels or know more than basic first aid?
Do you feel fairly streetwise/not easily flustered? How do you deal with extremely sad circumstances where villagers can't be saved etc etc? Do you have a coping mechanism?
Are you confident that you can deal with observing extreme poverty?
How resilient is your tummy? Do you recognise when you are feeling too hot/ probably have food poisoning and need to rehydrate pronto. You want to assist the community you are visiting, not hinder them! Get more jabs than you think you need (they take a while if you need boosters) and buy Malaria meds in the UK (I'd take my own basic sterile needles/IV/dressings too and make sure that somebody else knew how to use them).
In your situation I would have a jolly good think about why a visit from you and accommodation/travel logistics, personally, would "add value" to the lives of Liberians as opposed to sending them cash or goods with the money saved from the trip?
I can't imagine that you'll just be visiting for a week so, if I had a 5 year old back home, I would query why Liberia couldn't wait another 8-10 years.
Make sure that you are very clear why you are visiting Liberia and be prepared. Make sure your family understand your reasons too.