You always have to donate to an individual fundraiser. The donation will be shown as part of the total amount of the team, but it will be registered on a specific fundraiser. This is because of several reasons.
Though all members of a team participate in the same event, it is in fact possible that the event cooperates with more than one charity. And when somebody gives a donation, it is important that the donor can be perfectly sure about which charity will receive the donation. It is therefore not possible to give a donation to a team, as that would mean that it could have more than one receiver.
On top of that we always recommend people to make their own personal fundraiser, because of one simple reason: Two people with their own personal fundraisers will receive more donations in total, than two people with one joint fundraiser. This is because everybody have their own specific network, and the more personal and "you-focused" your fundraiser is, the more people will feel comfortable with it and donate.