TKD and Aikido are very different arts,you will have to try both Judo and Aikido to see which one you like , this is best. But if you did want to train in both you will have to find a way to integrate both with out conflicts, an example is TKD has wide stances, in Aikido stances used are ones that are very easy to move in and have good balance so a stance like say a deep stance or horse stance would not be suitable in most Aikido techniques. In fighting TKD might go for a straight punch one hit kill attack but in Aikido you might be told to do a Tenkan (turning exercise) and finish of with a ie kotegaeshi, this is stressed because you are very vunerable behind, if you try to take out someone in front of you a tenkan turn gives you a sight of your surroundings and you can use your oponnent as a shield or projectile. These are just little things but if you do it then you can choose what you like and what you dont like,even make your own style.