b1, b2 for parents

[shabnam]

hi. me and my husband are on j2 AND j1 visas respectively. im pregnant, in 6 month. and I want them to be here for my delivery to help me out. they are sponsoring for their own trip. but I would like to know what documents are we supposed to send? should we send all or some of the sponsor documents coz they are paying for their own expenses? please let me know.

[R78]

You may send them a copy of your visa page as proof that they are visiting their "family"
Self sponsoring is the best option. They need to show that they can afford their trip (tickets & insurance), will return after the visit (owning a house, job if they are still working etc.)
Usually B1/B2 for parents is quite easy.