custom product & checkout fields

Hi,

I ask this question as some plugins are not compatible with some themes. So I need your expertise on this.

1/What is the best plugin to add extra fields to a product page ? For example, “birthday package +3$”, “option 1, option 2 +20$, option 3 +30$”, “add your birthday card text” etc.
All those extras get counted into one total. This is something that can’t be done properly with product variations.

2/ What is the best pugin to add a “delivery date” field to the checkout page ?

thanks